EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, thalloid, with single-celled apical meristem, showing gravitropism; rhizoids +, unicellular; flavonoids + [absorbtion of UV radiation]; chloroplasts lacking pyrenoids; protoplasm dessication tolerant [plant poikilohydric]; cuticle +; cell walls with (1->4)-ß-D-glucans [xyloglucans], lignin +; several chloroplasts per cell; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles in vegetative cells 0, metaphase spindle anastral, predictive preprophase band of microtubules, phragmoplast + [cell wall deposition spreading from around the spindle fibres], plasmodesmata +; antheridia and archegonia jacketed, stalked; spermatogenous cells monoplastidic, centrioles develop de novo, associated with basal bodies of flagellae, multilayered structure +, proximal end of basal bodies lacking symmetry, stellate pattern associated with doublet tubules of transition zone; spermatozoids with a left-handed coil; male gametes with 2 lateral flagellae; oogamy; sporophyte dependent on gametophyte, embryo initially surrounded by haploid gametophytic tissue, plane of first division horizontal [with respect to long axis of archegonium/embryo sac], suspensor/foot +, cell walls with nacreous thickenings; sporophyte multicellular, with at least transient apical cell [?level], sporangium +, single, dehiscence longitudinal; meiosis sporic, monoplastidic, microtubule organizing centre associated with plastid, cytokinesis simultaneous, preceding nuclear division, sporocytes 4-lobed, with a quadripolar microtubule system; spores in tetrads, sporopollenin in the spore wall, wall with several trilamellar layers [white-line centred layers, i.e. walls multilamellate]; close association between the trnLUAA and trnFGAA genes on the chloroplast genome.
Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.
All groups below are crown groups, nearly all are extant; characters mentioned are those of the common ancestor of the group.
Abscisic acid, ?D-methionine +; sporangium with seta, seta developing from basal meristem [between epibasal and hypobasal cells], sporangial columella + [developing from endothecial cells]; stomata +, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and in rhizoids/root hairs; spores trilete; polar transport of auxins and class 1 KNOX genes expressed in the sporangium alone; MIKC, MI*K*C* and class 1 and 2 KNOX genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns.
[Anthocerophyta + Polysporangiophyta]: archegonia embedded/sunken in the gametophyte; sporophyte long-lived, chlorophyllous; sporophyte-gametophyte junction interdigitate, sporophyte cells showing rhizoid-like behaviour.
Sporophyte branched, branching apical, dichotomous; sporangia several; spore walls not multilamellate [?here].
EXTANT TRACHEOPHYTA / VASCULAR PLANTS
Photosynthetic red light response; water content of protoplasm relatively stable [plant homoiohydric]; control of leaf hydration passive; (condensed or nonhydrolyzable tannins/proanthocyanidins +); sporophyte soon independent, dominant, with basipetal polar auxin transport; vascular tissue +, sieve cells + [nucleus degenerating], tracheids +, in both protoxylem and metaxylem; endodermis +; root xylem exarch [development centripetal]; stem with an apical cell; branching dichotomous; leaves spirally arranged, blades with mean venation density 1.8 mm/mm2 [to 5 mm/mm2]; sporangia adaxial on the sporophyll, derived from periclinal divisions of several epidermal cells, wall multilayered [eusporangium]; columella 0; tapetum glandular; gametophytes exosporic, green, photosynthetic; stellate pattern split between doublet and triplet regions of transition zone; placenta with single layer of transfer cells in both sporophytic and gametophytic generations, embryonic axis not straight [root lateral with respect to the longitudinal axis; plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Branching ± indeterminate; lateral roots +, endogenous, root apex multicellular, root cap +; tracheids with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangia borne in pairs and grouped in terminal trusses, dehiscence longitudinal, a single slit; cells polyplastidic, microtubule organizing centres not associated with plastids, diffuse, perinuclear; male gametes multiflagellate, basal bodies staggered, blepharoplasts paired; chloroplast long single copy ca 30kb inversion [from psbM to ycf2].
Plant woody; lateral root origin from the pericycle; branching lateral, meristems axillary; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
EXTANT SEED PLANTS / SPERMATOPHYTA
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols [hence with p-hydroxyphenyl and guaiacyl lignin units, so no Maüle reaction]; root stele with xylem and phloem originating on alternate radii, not medullated [no pith], cork cambium deep seated; arbuscular mycorrhizae +; shoot apical meristem interface specific plasmodesmatal network; stem with vascular cylinder around central pith [eustele], phloem abaxial [ectophloic], endodermis 0, xylem endarch [development centrifugal]; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaves with single trace from vascular sympodium [nodes 1:1]; stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; buds axillary (not associated with all leaves), exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, blade simple; plant heterosporous, sporangia borne on sporophylls; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], exine and intine homogeneous; ovules unitegmic, parietal tissue 2+ cells across, megaspore tetrad linear, functional megaspore single, chalazal, lacking sporopollenin, megasporangium indehiscent; pollen grains land on ovule; gametophytes dependent on sporophyte; male gametophyte development initially endosporic, tube developing from distal end of grain, gametes two, developing after pollination, with cell walls; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large" [ca 8 mm3], but not much bigger than ovule, with morphological dormancy; embryo cellular ab initio, endoscopic, plane of first cleavage of zygote transverse, suspensor +, short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], white, cotyledons 2; plastid transmission maternal; ycf2 gene in inverted repeat, whole nuclear genome duplication [zeta duplication], two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.
ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common [positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0, exodermis +; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, associated gelatinous fibres [g-fibres] with innermost layer of secondary cell wall rich in cellulose and poor in lignin; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cell and sieve tube from same mother cell; sugar transport in phloem passive; nodes 1:?; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance to increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, venation hierarchical-reticulate, secondary veins pinnate, veins (1.7-)4.1(-5.7) mm/mm2, endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, ± haplomorphic, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P +, members each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], ± embedded in the filament, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally, endothecium +, endothecial cells elongated at right angles to long axis of anther; (tapetum glandular), cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine +, thin, compact, lamellate only in the apertural regions; nectary 0; carpels present, superior, free, several, ascidiate, with postgenital occlusion by secretion, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry [not secretory]; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, functional megaspore, chalazal, lacking cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; supra-stylar extra-gynoecial compitum +; ovule not increasing in size between pollination and fertilization; pollen grains land on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, flagellae 0, double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; seed exotestal, much larger than ovule at time of fertilization; endosperm diploid, cellular, heteropolar [micropylar and chalazal domains develop differently, first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous; dark reversal Pfr → Pr; Arabidopsis-type telomeres [(TTTAGGG)n]; 2C genome size 1-8.2 pg [1 pg = 109 base pairs], whole nuclear genome duplication [epsilon duplication]; protoplasm dessication tolerant [plant poikilohydric]; ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]].
[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.
[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood +; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; carpels plicate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.
[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [possible position]; pollen tube growth intra-gynoecial; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid.
[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (extra-floral nectaries +); (veins in lamina often 7-17 mm/mm2 or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).
[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0.
EUDICOTS: (Myricetin, delphinidin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; K/outer P members with three traces, ("C" +, with a single trace); A few, (polyandry widespread, initial primordia 5, 10, or ring, ± centrifugal), filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here]; seed coat?
[PROTEALES [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).
[TROCHODENDRALES [BUXALES + CORE EUDICOTS]]: benzylisoquinoline alkaloids 0; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial rps2 gene lost.
[BUXALES + CORE EUDICOTS]: ?
CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one place]; micropyle?; whole nuclear genome duplication [palaeohexaploidy, gamma triplication], PI-dB motif +, small deletion in the 18S ribosomal DNA common.
[ROSIDS ET AL. + ASTERIDS ET AL.] / PENTAPETALAE: root apical meristem closed; (cyanogenesis also via [iso]leucine, valine and phenylalanine pathways); flowers rather stereotyped: 5-merous, parts whorled; P = calyx + corolla, calyx enclosing the flower in bud, sepals with three or more traces, petals with a single trace; stamens = 2x K/C, in two whorls, internal/adaxial to the corolla whorl, alternating, (numerous, but then usually fasciculate and/or centrifugal); pollen tricolporate; G , G  also common, when [G 2], carpels superposed, compitum +, placentation axile, style +, stigma not decurrent; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]; RNase-based gametophytic incompatibility system present; floral nectaries with CRABSCLAW expression; (monosymmetric flowers with adaxial/dorsal CYC expression).
Age. Soltis et al. (2008: a variety of estimates) suggested that these two large clades diverged 128-114(-84) m.y.a., and similar ages of (131-)120, 117(-112) and (132-)125, 101(-97) m.y. are proposed by Bell et al. (2010). Wikström et al. (2001) suggested ages of (130-)125, 114(-109) m.y..
Evolution. Divergence & Distribution. Doyle (2013) suggested that the distinctive pentapetalous flower descibed above evolved from a wind-pollinated, probably dimerous morphology.
Harmomegathic movements of triaperturate pollen grains are discussed by Halbritter and Hesse (2004).
Pollination Biology. For the evolution of the gametophytic incompatibility system, perhaps a precursor to the sporophytic system (although the two may in fact merely be qualitatively different), see Igic and Kohn (2001: phylogeny of RNases), Steinbachs and Holsinger (2002), Igic et al. (2006), Franklin-Tong and Franklin (2003), Charlesworth et al. (2005) and Hiscock and Tabah (2003).
Genes & Genomes. There has been duplication of all four MADS-box gene classes (A, B, C, E) somewhere around here, and also the floral symmetry genes CYCLOIDEA and DIVARICATA (e.g. Boyden et al. 2010).
Chemistry, Morphology, etc. Both sepals and petals of core eudicots may be derived from bracts, bracts and sepals often having three or more traces, petals a single trace (Ronse de Craene (2007); only cases where the vasculature is other than this are mentioned below.
[DILLENIALES [SAXIFRAGALES [VITALES + ROSIDS s. str.]]]: stipules + [usually apparently inserted on the stem].
Age. Moore et al. (2010) suggest an age of (112-)108(103) m.y. for this node (if it exists).
[SAXIFRAGALES [VITALES + ROSIDS]] / ROSANAE Takhtajan / SUPERROSIDAE: ? Back to Main Tree
Age. The age of this node has been estimated at (125-)121, 111(-107) m.y. (Wikstr&m et al. 2004); the age in Anderson et al. (2005: see positions of Crossosomatales included) is ca 108 m.y. and it is ca 160 m.y. in Z. Wu et al. (2014: [Vitales + Saxifragales] sister to rest, ca 151 m.y.a. divergence between the two). Magallón and Castillo (2009) provide estimates of around 114.5 m.y., Moore et al. (2010: 95% highest posterior density) an age of (111-)108(-103) m.y.; ages of (135-)128, 117(-111) m.y. are suggested by Bell et al. (2010), (112-)107(-101) m.y. by N. Zhang et al. (2012), and 110.5 m.y. by Magallón et al. (2013) - or ca 58 m.y. (Palazzesi et al. 2012, but c.f. Sytsma et al. 2014 - ca 104 m.y.).
Fossils are somewhat younger, and those assignable to rosids as a whole are ca 94 m.y.o., and those to Saxifragales ca 90 m.y. old (Crepet et al. 2004).
Evolution. Divergence & Distribution. Much crown group diversification within this clade probably occurred within a narrow time interval of 5-15 m.y. around 117-93 m.y.a. in the late Aptian early Turonian (Wang et al. 2009).
Ecology & Physiology. Increase in seed size is especially distinctive at this node, and this is associated with large leaf size; plants commonly grow in equatorial areas that are both warm and well-watered (Cornwell et al. 2014: c.f. Saxifragales).
Smets et al. (2003) characterise the rosids as having receptacular nectaries; but Vitales have gynoecial nectaries and Proteaceae, and perhaps Sabiaceae, have receptacular nectaries (Smets 1988). For CRABSCLAW expression in the floral nectaries, see Damerval et al. (2013). A relatively large embryo over half the length of the seed may be a feature of this clade (Forbis et al. 2002), although there is considerable variation in Saxifragales and Vitales have small embryos. Here this character has been pegged at a lower level in the phylogeny (see core rosids).
Plant-Animal Interactions. Butterfly caterpillars are common on members of the group, occurring about twice as frequently as might be expected going by species number alone, but the tree habit is also common here, and trees perhaps can support a correspondingly disproportionately large number of larvae (Janz & Nylin 1998). However, Menken et al. (2009; see also Ward et al. 2003) reported on an extensive survey of larval host plants of British lepidoptera which they thought could be extended - with care - more globally, noting that caterpillars of basal Lepidoptera-Glossata (butterflies and moths with a coilable proboscis) tended to be found on woody rosid I (Fabidae) plants, normally as leaf miners or other non-exposed life styles (see also Ward et al. 2003). Since mines attributed to basal glossatan Neptulicidae have been reported from fossil magnoliid and protealean leaves, among others (see Menken et al. 2009), and these plants have a rather different chemistry from that of the rosids, the deep history of such lepidoptera-plant associations is unclear.
Genes & Genomes. For a possible genome duplication, see Tuskan et al. (2006) and Jaillon, Eury et al. (2007); it is probably to be placed immediately basal to the core eudicot node. Where the loss of the chloroplast infA gene is to be placed is unclear (see Millen et al. 2001).
Chemistry, Morphology, etc. Taxa that have cuticle wax platelets as rosettes are scattered through this group, but they are especially common in Fabaceae and there are also several Malpighiales (see Ditsch & Barthlott 1997 for details). Distinctive mucilage cells with a much thickened mucilaginous inner periclinal wall and distinct cytoplasm are found in flowers especially in this broader group, but they are not yet reported from Geraniales (Matthews & Endress 2006b). The sepals characteristically have three traces from three gaps; in several more basal eudicot clades the outer perianth/sepals have only a single gap (von Balthazar and Endress 2002 - see also Ranunculales). Petal development is often retarded relative to that of other parts of the flower (also in Cabomba and Saruma).
Phylogeny. Basal relationships within rosids remain somewhat unclear. Hilu et al. (2003: matK analysis, Schumacheria [one member of Dilleniaceae included in the study] was firmly associated with Ericales...) found a possible set of relationships [Rosids [[Dilleniacaeae + Vitaceae] [Saxifragales [Santalales [Berberidopsidales [Caryophyllales + Asterids]]]]]]. Nickrent et al. (2005) also found the position of Saxifragales to be particularly uncertain, although Vitales again tended to go with rosids. Recently, Soltis et al. (2007a) found a grouping [Saxifragales [Vitales + rosids]], both groupings with 1.0 p.p. (see also Zhu et al 2007, but little support). Earlier work had suggested similar relationships, thus Saxifragales were sister to the rest of the group (e.g. P. Soltis et al. 1999: Vitales not included), albeit with weak support. Studies on the duplication of the RPB2 gene and subsequent loss of one of the copies (Oxelman et al. 2004; Luo et al. 2007) suggest that Saxifragales and Rosids are linked by loss of the -I copy, which also has occurred in Santalales and Caryophyllales, but not Vitales, Berberidopsidales, Gunnerales or Dilleniales, which have all lost the RPB2-D copy. Saxifragales and Vitales were found to be successively sister to all eudicots minus Gunnerales (mitochondrial gene only), or to all rosids, but with little support (Zhu et al. 2007).
Moore et al. (2010, 2011) found that although [Saxifragales, Vitales, rosids] formed a strongly-supported clade, it was unclear whether Vitales were sister to Saxifragales, to rosids, or to [Saxifragales + rosids]; support for the latter position increased with reduced taxon sampling. Moore et al. (2010) also recovered a [Saxifragales + Vitales] clade sister to rosids in maximum likelihood but not in maximum parsimony analyses, and this also appeared in most analyses in Ruhfel et al. (2014), in both nuclear and chloroplast, but not in mitochondrial, analyses in Sun et al. (2014), and in the chloroplast genome analyses of Z. Wu et al. (2014).
Hengcheng Wang et al. (2009: Dilleniales not included) in a 43,000 bp analysis, largely of chloroplast sequences, found substantial resolution within rosids s.l., and the relationships that they suggest, [Saxifragales [Vitales [rosid I/fabids + rosid II/malvids]]], are followed here, although the position of Vitales is only moderately supported (72% bootstrap in a ML analysis); they analysed a twelve-gene and inverted repeat data sets separately and in combination, preferring ML over MP analyses. The topology in Davies et al. (2004), Bell et al. (2010) and Soltis et al. (2011) is similar. Saxifragales are also well supported as sister to [Vitales + rosids] in the 12-gene plus plastid inverted repeat analyses of Wang et al. (2009). Vitales may well be sister to the other rosids s. str. (e.g. Jansen et al. 2007), although support was only weak in Wang et al. (2009). A palaeohexaploidy event seemed to link Vitales with rosids, but the sampling in major core eudicot clades was very poor (Jaillon, Eury et al. 2007); that event may be a synapomorphy for core eudicots (see above).
Finally, Saxifragales have sometimes been found to be sister to a [Berberidopsidales ... asterid] clade, although with vanishingly low support, and Vitales sister to a rosid clade, but with scarcely any stronger support (Qiu et al. 2010). Crossosomatales were in a clade basal to Caryophyllales, while other relationships in the rosid II clade were somewhat scrambled, although again with little support (Qiu et al. 2010). The relationships [[Vitaceae + Saxifragales] [Caryophyllales + rosids]] have also popped up (N. Zhang et al. 2012; Sun et al. 2104: mitochondrial and nuclear data) as have the relationships [Vitales [rosids + asterids]] (Wickett et al. 2014: transcriptome analyses), but this latter may be a sampling problem, since no Saxifragales, Dilleniales, etc., were included.
See the Dilleniales page for further discussion on major patterns of relationships within Pentapetalae and the rosid node for major patterns in relationships within the rosids.
Classification. The circumscription of the rosids could usefully be expanded to include both Saxifragales and Vitales if they form a single clade (see above); they are morphologically quite similar.
SAXIFRAGALES Berchtold & J. Presl Main Tree, Synapomorphies.
Ellagic acid, myricetin, flavonols +, (silicon concentration high [?level]); (tension wood +); branching from the previous flush [woody members]; cuticle waxes as clustered tubules; petiole bundle annular; lamina margins serrate, teeth with gland broadening distally and with apical foramen, higher order lateral veins joining it; anthers basifixed, with basal pit, sagittate; carpels free, at least apically, styluli short, stigmas decurrent, at most slightly wet; ovules ³2/carpel, with bistomal micropyle, (outer integument largely dermal in origin); fruit dry; seeds ± exotestal; embryo size?; unique 1 BP [adenosine] insertion in 18S rDNA. - 15 families, 112 genera, 2,500 species.
Age. Jian et al. (2006, esp. 2008) estimate the crown-group age for Saxifragales at 103-83 m.y..
Note: Possible apomorphies are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is partly because many characters show considerable homoplasy, in addition, basic information for all too many is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there is the not-so-trivial issue of how ancestral states are reconstructed (see above).
Evolution. Divergence & Distribution. Saxifragales contain ca 1.3% of eudicot diversity. They have a very poor representation in the tropics in general, which makes the inclusion of the small but lowland tropical Peridiscaceae as sister to the rest (see below) the more notable. Because many relationships within Saxifragales were difficult to resolve, it was suggested that they represented an ancient and rapid radiation (Fishbein et al. 2001; Fishbein & Soltis 2004). More recently Jian et al. (2006, esp. 2008) estimated that early diversification in the clade perhaps occurred over a period as short as 3-6 m.y., while Hermsen et al. (2006b: topology quite resolved, different in detail from that adopted here, support slight) thought that much diversification occurred around 90-84 m.y.a. in the Late Cretaceous. D. Soltis et al. (2013) looked at diversification in Saxifragales in the context of a 900+-species supermatrix, focusing particularly on woody<->herbaceous and annual<->perennial transitions.
Saxifragales have notably small seeds compared with those of other angiosperms (Linkies et al. 2010), although this is not so for Peridiscaceae, so this character is pegged at the next node up.
D. Soltis et al. (2007b), Endress (2010c) and Carlsward et al. (2011) have all suggested possible apomorphies for the clade - or at least features common in the clade - other than those given above, while Hermsen et al. (2006b, see list of characters there) thought that Saxifragales lacked any "diagnostic" morphological features. Carlsward et al. (2011) suggest apomorphies for all internal branches of Saxifragales, and many of these are flagged as such below (pollen characters are not yet included). Doyle (2012) suggested that tricolpate pollen was "retained" in many Saxifragales.
Plant-Animal Interactions. Caterpillars of Papilionidae-Parnassiinae are quite common here (Simonsen et al. 2011; Condamine et al. 2011).
Chemistry, Morphology, etc. Roots are diarch (Van Tieghem & Douliot 1888). Saxifragales commonly have scalariform perforation plates, lateral pitting that is mostly scalariform or opposite, bordered pits, etc., but whether these are synapomorphies is unclear (Jian et al.  characterise the largely unresolved woody members and the Saxifraceae + Crassulaceae clades in terms of their wood anatomy). Leaf teeth are basically rosid, although those of Cercidiphyllum are described as being more or less chloranthoid (not very different), while Hamamelidaceae can have teeth with a clear, glandular apex (fothergilloid) and those of Altingiaceae are platanoid (basically, the higher order lateral veins do not quite make it to the tooth - Hickey & Wolfe 1975; Tetracarpaea is similar, also lacking such veins - Hils et al. 1988). Despite appearances, the floral apex in nearly all taxa studied is reportesd to be flat or concave (Fishbein et al. 2000; Soltis & Hufford 2002; D. Soltis et al. 2003b; Soltis et al. 2005b), although Wurdack and Davis (2009) suggested that this was not the case for Peridiscaceae.
For information on the hamamelids as it was beginning to be realised that they might have to be split, see Crane and Blackmore (1989). For pollen, see Hideux and Ferguson (1976), Zavada and Dilcher (1986); floral anatomy and morphology, Gaümann (1919), Bensel and Palser (1975a-d), Hufford and Endress (1989), Drinnan et al. (1995), Fishbein et al. (2000); for chemistry, Giannasi (1986), Jay (1971); for anatomy, Watari (1939), Ramamonjiarisoa (1980), Cutler and Gregory (1998); for seed coat, Krach (1976); and for general morphology, see Hermsen et al. (2006b).
Phylogeny. Saxifragales as circumscribed here have long suggested in molecular phylogenies (e.g. D. Soltis et al. 1997; D. Soltis & P. Soltis 1997), although support is not always very strong (D. Soltis et al. 2013).
Within Saxifragales relationships other than the Saxifragaceae/Crassulaceae clade were unclear for some time, and even now many of the deeper nodes remain poorly supported (D. Soltis et al. 2013). However, support for the Crassulaceae et al. and Saxifragaceae et al. clades and the relationships within them is generally strong. The relationships [[Crassulaceae [Tetracarpaeaceae [Penthoraceae + Haloragaceae]] [[Saxifragaceae [Iteaceae + Pterostemonaceae]]] Grossulariaceae]] were found by Morgan & Soltis (1993); support for a [Pterostemon + Itea] clade (= Iteaceae) is strong (e.g. Soltis et al. 2007a: see below). Aphanopetalum (ex Cunoniaceae) is to be included in the Crassulaceae et al. clade.
Although Hilu et al. (2003: matK) did not recover the Saxifragaceae/Crassulaceae clade, there was no strong support for an alternative placement; Cercidiphyllaceae and Daphniphyllaceae were sister taxa, with moderate jacknife support. Hermsen et al. (2006b), who included both molecular and morphological (the latter also from selected fossils) data, also recovered a [Crassulaceae et al. + Saxifragaceae et al.] clade, while all other families were in a clade sister to this. [Paeonia + Daphniphyllum] and [Cercidiphyllaceae + Altingiaceae] were clades, but with very weak support (<50% bootstrap). Paeonia was linked with moderate support to the Crassulaceae clade, or, more weakly, with the Crassulaceae + Saxifragaceae clades in some analyses in Fishbein et al. (2001); the latter relationship also appeared in a study by Fishbein and Soltis (2004).
In none of these analyses were Peridiscaceae included; this family was an unexpected addition to Saxifragales. Peridiscaceae had been placed in Malpighiales by Savolainen et al. (2000a: see A.P.G. II 2003). However, Davis and Chase (2004; see also Soltis et al. 2007a) found that the family belonged here, adding Soyauxia, previously placed in Medusandraceae, while Wurdack and Davis (2009) added Medusandra. Paeonia was linked with low support to Peridiscus itself by Davis and Chase (2004). D. Soltis et al. (2007b) were unable to recover stable relationships among the woody Saxifragales, long branch attraction (to Paeoniaceae and Peridiscaceae) possibly occurring; depending on the analysis, a [Peridiscaceae + Paeoniaceae] clade made Hamamelidaceae paraphyletic, or Peridiscaceae were sister to all other Saxifragales. Despite the addition of more data, Jian et al. (2006) still found it difficult to resolve relationships between the woody members, although it appeared that Peridiscaceae might be sister to the rest of the order, and Paeoniaceae sister to the Crassulaceae and Saxifragaceae groups. Similar relationships were recovered by Soltis et al. (2011, see also Moore et al. 2011), but support for the position of Paeoniaceae was weak; other relationships with Saxifragales that they found agree with the topology described below. Li (2008) also found little support for many relationships in the order, including the association of Paeoniaceae with the Crassulaceae group that appeared in some analyses.
However, Jian et al. (2008: see also Qiu et al. 2010, slight differences [placement of Hamamelidaceae]), using a variety of large data sets (some with over 50,000 bp) and analyeses, found strong maximum likelihood and Bayesian support for the topology used here, although Paeonia in particular moved around the tree in some parsimony analyses. There is little morphological support for the basal branches, pretty much par for the course, although characters can be optimised to positions on a number of the shallower branches (c.f. Hermsen et al. 2006b). A study by Qi et al. (2012) that focused on Cercidiphyllum found a rather different set of relationships, including the paraphyly of Hamamelidaceae, but posterior probabilities were low.
Some molecular analyses have placed the hitherto unplaced Cynomoriaceae in Saxifragales, perhaps in the Crassulaceae area, although with little support (Nickrent 2002; Nickrent et al. 2005), however, Barkman et al. (2007) found no support for a position in this order - but none for any particular position at all. A position in Saxifragales was rejected by Jian et al. (2008), who preferred to place them in Santalales; Balanophoraceae, with which Cynomoriaceae were linked in the past, are also to be included there (see also Nickrent et al. 2005). Recently Cynomoriaceae have been placed in Rosales as sister to Rosaceae based on analysis of chloroplast inverted repeat sequences (Moraceae were the only other family in the order examined: see also the Rosales page), and with strong support; Cynomoriaceae were certainly to be excluded from Saxifragales (good sampling) and several other rosid orders (Z.-H. Zhang et al. 2009; see also Moore et al. 2011). Finally, depending on the mitochondrial gene analyzed by Qiu et al. (2010), Cynomoriaceae were placed with Saxifragales (matR, nad5) or Sapindales (atp1, rps3). Based on ages alone, Cynomoriaceae may be sister to all other Saxifragales, in which they were included; although Paeoniaceae and Altigniaceae were the only other Saxifragales in the study, there were representatives of the other clades to which Cynomoriaceae might be related (Naumann et al. 2013). Further studies are needed and the inclusion of Cynomoriaceae here needs confirmation.
Previous Relationships. Saxifragales include Hamamelidaceae, thought to be a key group classically linking the Englerian Amentiferae (usually dioecious or monoecious woody plants with an ament, or catkin, with small flowers, and sometimes believed to be primitive), to "dicots" with more conventional flowers (e.g. Endress 1967; Frohne & Jensen 1992). However, the old Amentiferae, included in Cronquist's (1981) Hamamelidae, are now in several bits, mostly in the rosids, of which one is here - see also Fagales, the major part of Amentiferae, Malpighiales (Salicaceae), Rosales ("Urticales"), etc. (Qiu et al. 1998a). For the woody Saxifragaceae, now similarly widely distributed, see below; many iridoid-positive and/or tenuinucellate members are now in the asterids, but most iridoid-negative, herbaceous and/or crassinucellate members remain here. Ironically, three families of Saxifragales s. str. are reliably reported to have iridoids (how many origins?) and are the only families outside asterids with them. Daphniphyllanae, Saxifraganae and Hamamelidanae, in which Takhtajan (1997) placed most of the families that are in Saxifragales here, are all in his Hamamelididae.
Includes Altingiaceae, Aphanopetalaceae, Cercidiphyllaceae, Crassulaceae, Cynomoriaceae, Daphniphyllaceae, Grossulariaceae, Haloragaceae, Hamamelidaceae, Iteaceae, Paeoniaceae, Penthoraceae, Peridiscaceae, Saxifragaceae, Tetracarpaeaceae.
Synonymy: Hamamelidineae Thorne & Reveal - Altingiales Doweld, Cercidiphyllales Reveal, Crassulales Link, Cynomoriales Burnett, Daphniphyllales Hurusawa, Fothergillales Link, Grossulariales Berchtold & J. Presl, Haloragales Link, Hamamelidales Link, Iteales Doweld, Medusandrales Brenan, Paeoniales Heinze, Peridiscales Doweld, Sedales Reichenbach f., Sempervivales Berchtold & J. Presl - Daphniphyllanae Takhtajan, Hamamelidanae Takhtajan, Paeonianae Doweld, Saxifraganae Reveal - Hamamelididae Takhtajan, Paeoniidae C. Y. Wu - Crassulopsida Brongniart, Hamamelidopsida Brongniart, Saxifragopsida Brongniart
PERIDISCACEAE Kuhlmann, nom. cons. Back to Saxifragales
Trees; plants Al-accumulators, ?chemistry; vessel elements with scalariform perforation plates; apotracheal (paratracheal, diffuse) parenchya +; secretory canals + [Medusandra]; petiole bundles with wing bundles [Soyauxia], also an adaxial plate [Peridiscus] or an adaxial [Whittonia] or medullary [Medusandra] annular bundle; crystals +; hairs unicellular, lignified [Medusandra]; epidermal wax crystals in rosettes; leaves two-ranked, (spiral), lamina teeth ?morphology, (margin entire), secondary veins palmate, petiole pulvinate [Peridiscus, Medusandra], stipule single and adaxial, or paired and lateral; inflorescences axillary, racemose(-spicate) or fasciculate, flowers small; P 4-7; A many, at most slightly connate basally, (anthers monothecal); nectary large, annular, hairy or not, or K open, C +; A 5, opposite C, staminodes 5, long, hairy, opposite K; nectary 0 [Medusandra]; G [3-4], ± sunken in disc or not, 1-locular, (placentation free central), stigmas punctate; ovules 1-2(-3)/carpel [6-8 in total], apical, pendulous, epitropous; fruit a drupe or capsule, wall expanding early [Medusandra], P deciduous or K much enlarged, accrescent, recurved (Medusandra); seed 1, large, coat tanniniferous, walls thin, ± collapsed; endosperm ?development, copious, cell walls thick, pitted, embryo very small, cotyledons foliaceous; n = ?
4[list]/11. South America, tropical W. Africa (map: from Heywood 2007; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010).
Chemistry, Morphology, etc. Peridiscaceae are a very poorly known and superficially heterogeneous group; I have not seen Whittonia, but Metcalfe (1962) gives some details of its anatomy. The vascular pitting of Medusandra is scalariform and the pits are bordered (Metcalfe 1952). Note that the leaves are almost certainly simple, not unifolioliate (c.f. Brenan 1952; Hutchinson 1973); the rather swollen apex of the petiole is like that of many Euphorbiaceae, Hydnocarpus, Octoknema, etc., which are not usually described as being possibly unifoliolate. Petiole anatomy in the region of the pulvinus is complex. For epidermal wax crystals, see Ditsch and Barthlott (1997). The bracteoles are often inconspicuous (c.f. Cronquist 1981).
Peridiscus and Whittonia have monothecal anthers, probably derived within the family. The flowers of Medusandra have long and conspicuous staminodes borne opposite the sepals, hence the generic name. The basic seed morphology/anatomy of Soyauxia and Peridiscus, from either side of the Atlantic, are almost identical, although the two are vegetatively very different - Peridiscus is sometimes even identified as Menispermaceae!
See Metcalfe (1952b, 1962) and Miller (1975) for anatomy and Soltis et al. (2007b) and Bayer and Dressler (2014) for general information.
Phylogeny. Relationships are [Medusandra [Peridiscus + Soyauxia]] (Wurdack & Davies 2009).
Previous Relationships. Peridiscaceae were included in Violales-Flacourtiaceae by Takhtajan (1997), and a similar position was suggested by A.P.G. III (2003); Soyauxia in particular has been associated with Medusandraceae or with Flacourtiaceae (Malpighiales). Medusandra itself was tentatively included in Malpighiales by Soltis et al. (2005b), certainly, the serrate leaf blades and the cauline stipules suggest relationships other than to Santalales or Santalanae (c.f. Cronquist 1981; Takhtajan 1997; Thorne 2007).
Synonym: Medusandraceae Brenan, nom. cons.
[[Paeoniaceae [Altingiaceae [Hamamelidaceae [Cercidiphyllaceae + Daphniphyllaceae]]]] [[Crassulaceae [Aphanopetalaceae [Tetracarpaeaceae [Haloragaceae + Penthoraceae]]]] [[Iteaceae [Grossulariaceae + Saxifragaceae]]]: floral apex flat-concave early in development; hypanthium +/G often (semi-)inferior.
Age. Magallón and Castillo (2009) estimated an age of ca 106.7 m.y. for this node, Bell et al. (2010) an age of (111-)103, 95(-92) m.y.. Other estimates are from Wikström et al. (2001, 2004) at (116-)111, 92(-87) m.y.a. and Anderson et al. (2005) at ca 102 m.y. ago.
Evolution. Divergence & Distribution. This clade is characterised by having notably small seeds (Moles et al. 2005a; Sims 2012: as Saxifragales, but Peridiscaceae not included).
[Paeoniaceae [Altingiaceae [Hamamelidaceae [Cercidiphyllaceae + Daphniphyllaceae]]]]: buds perulate; leaves with basically palmate venation; stigma ± decurrent; mitochondrial coxII.i3 intron 0.
Age. The age of this clade is estimated to be around 72.6 m.y. (Naumann et al. 2013).
PAEONIACEAE Rafinesque, nom. cons. Back to Saxifragales
Perennial herbs, shortly rhizomatous, to shrublets; ethereal oils, flavones +, hydrolysable and non-hydrolysable tannins 0; cork "subcortical" [Tiagi 1970]; stem with cortical vascular bundles; vessel elements with simple or scalariform perforation plates; nodes also 5:5; calcium oxalate as crystals; wax tubules with palmitone predominating; palisade mesophyll with arm cells; indumentum 0 (hairs +, unicellular); leaves spiral, compound, ultimately ternate, lamina vernation variable, leaf base broad, stipules 0; inflorescence terminal, flowers 1-few; flowers large [³5 cm across], with cortical vascular system; P +, spiral, 3:3 vascularization, "K" (3-)5(-7), tough, "C" 5-8(-13), not sharply distinguished; A many, from 5 trunk bundles continuing spiral of P, centrifugal, anthers with basal pits?; G free, (2) 3-5(-15), stylulus 0, stigma expanded, rather oblique, wet; ovules usu. many/carpel, micropyle exo(bi)stomal, outer integument 10-20 cells across, inner integument ca 3 cells across, parietal tissue ca 5 cells across, nucellar cap ca 12 cells across, nucellus mostly absorbed before anthesis; megaspore mother cells several, embryo sac often more than 1, elongate; fruit a follicle, K persistent; funicle fleshy, with apical rim-aril (0); testa fleshy, vascularized, exotestal cells palisade, variously thickened, the hypodermis palisade, ± lignified, (some mesotesta thickened); endosperm with amyloid [xyloglucans], chalazal endosperm haustorium +, zygote initially coenocytic, several embryos initially developing, one matures, minute; n = 5, chromosomes 10-15 µm long; germination hypogeal; mitochondrial coxII.i3 intron 0.
1[list]/33. N. Temperate, especially East Asia (map: from Stern 1946; Hultén & Fries 1986). [Photo - Fruit]
Evolution. Divergence & Distribution. For the evolution and biogeography of the genus, see Sang et al. (1997).
Seed Dispersal. The testa is thick, fleshy and coloured, and in some species at least its blackish colour contrasts with the red of the testa of partly developed and unfertilized seeds when the follicle opens. The funicle is also fleshy.
Chemistry, Morphology, etc. According to Hiepko (1965, see also Endress 2010c) Paeonia lacks petals - presumably because of the spiral arrangement and vasculature of the perianth members. There is a prominent lobed disc, but apparently it does not secrete nectar (Hiepko 1966). Johri et al. (1992) called the micropyle exostomal, however, the inner integument, too, partly forms the micropyle.
Both embryo sac and embryo development are very distinctive. The embryo sacs (there is often more than one per ovule) develop from megaspore mother cells that are deeply embedded in a massive nucellus plus nucellar cap, and they elongate considerably towards the micropyle as they develop; the secondary endosperm nucleus is huge (see e.g. Yakovlev & Yoffe 1957; Cave et al. 1961; Walters 1962). The funicle is also fleshy, and there may be a small rim aril at the apex. There is no tegmen.
For general information, see Tamura (2006), for the perianth, see also Brouland (1935); for general floral morphology, see Hiepko (1964, 1966) and Leins and Erbar (1991); Yakovlev and Yoffe (1957), Tiagi (1970) and Takhtajan (1988) provide much information on ovules and seeds. For an account of the genus, see Hong (2012).
Previous Relationships. Paeoniales were included in Ranunculidae (Takhtajan 1997), and a relationship between Paeoniaceae and Ranunculaceae in particular has often been suggested (Takhtajan 1997; Mabberley 1997 included Glaucidium [see Ranunculaceae here] in Paeoniaceae) because of gross floral similarities between the two. However, they differ in the nature of the petals and nectaries, the development of the androecium, numerous embryological features, etc. (e.g. Tiagi 1970); there are no dipteran agromyzid leaf miners on Paeoniaceae, although they are common on Ranunculaceae. Dilleniales, in which Paeoniaceae were placed by Cronquist (1981; see Corner 1946), have multistaminate and centrifugal androecia, but differ in gynoecial development, nectary morphology, etc.
[Altingiaceae [Hamamelidaceae [Cercidiphyllaceae + Daphniphyllaceae]]]: (route I iridoids +); cuticle waxes as tubules, nonacosan-10-ol the main wax; buds perulate; inflorescence racemose, flowers sessile; anthers ± valvate, connectives apically protruding; seeds winged; embryo long; germination epigeal and phanerocotylar.
Age. Moore et al. (2010: 95% HPD) suggested crown group ages of (103-)98(-94) m.y. for this node.
Evolution. Divergence & Distribution. Maslova (2010; see also Maslova et al. 2012) saw fossil Platanaceae and Hamamelidaceae, in particular Hamamelidaceae-Altingioideae, as being related and springing from a polymorphic ancestral group. Maslova's Hamamelidales included Hamamelidaceae, with a number of fossil genera, Platanaceae and several more fossil genera, and Bogutchantaceae (for further details, see Platanaceae) while Sarbaicarpaceae N. Maslova and Kasicarpaceae N. Maslova were both placed in the extinct order Sarbaicarpales N. Maslova, part of the immediately larger group.
Variation in this whole group is complex, and whether some characters reflected common ancestry or parallel variation was unclear (Maslova 2010: p. 1456 for a summary). Vavilov's Law of parallel variation was invoked (Maslova 2010: table 2), and it helped explain the "isomorphic polymorphisms" observed in platanoids and altingioids. Maslova (2010) was inclined to reject molecule-based hypotheses of relationships, and Proteaceae barely entered into the discussion; it is unclear what to make of these fossils and ideas.
Pollination Biology. There are a number of reports of delayed fertilization from members of all four families, although not in Paeonia (Endress 2110c, but esp. Sogo & Tobe 2006d and references), hence the placement of this feature here.
Chemistry, Morphology, etc. Raffinose and stachyose are common oligosaccharides in phloem exudate in this clade (Daphniphyllaceae not studied: Zimmermann & Ziegler 1975). Hufford and Endress (1989; see also Hersen et al. 2006b) discuss anather morphology and anatomy in detail; members of this clade can have obviously valvate anthers, as in Hamamelidoideae, or the stomium may simply divide at the two ends of the theca, or at least at the base of the theca. Wheeler et al. (2011) summarize what is known of wood anatomy in the clade.
ALTINGIACAEAE Horaninow, nom. cons. Back to Saxifragales
Trees, evergreen or deciduous; resins, route I iridoids +; secretory canals + [with resins]; petiole with 3-5 annular bundles (with medullary bundles); stomata paracytic; leaves spiral, lamina lobed, vernation flat, lobes conduplicate, stipules on leaf base; plant monoecious, inflorescence ± capitate; P 0; staminate flowers: A 4-10, (anthers with longitudinal slits), ?filament length; pollen grains polyporate, spherical, surface fine-reticulate; pistillode +; carpellate flowers: intercarpellary protrusions + [= sterile flowers]; G , unsealed, (semi)inferior, (transverse), stigmas with multicellular protrusions, but no papillae; ovules 20</carpel [only the lower ones fertile], straight, (micropyle endostomal), outer integument ca 2 cells across, inner integument ca 5 cells across; fruit a septicidal (and loculicidal) capsule; exotesta lignified or not, mesotesta ± sclerotic, endotestal cells oblong, lignified; endosperm slight; n = 15, 16.
1[list]/13. E. Mediterranean, East Asia to Malesia, Central America (map: see Vink 1957; Wood 1972; Rzedowski 1978; esp. Ickert-Bond et al. 2005). [Photos - Collection]
Age. Ickert-Bond and Wen (2006) suggested that the crown-group age for the family can be dated to somewhere between 54 and 19.5 m.y. ago.
The fossil Microaltingia (ca 90 m.y.o.) has prolate, tricolpate pollen grains with a coarsely reticulate exine, a more or less superior ovary, ovaries with 8 or more ovules per carpel, and perhaps unwinged seeds; it may have been pollinated by insects (Z.-K. Zhou et al. 2001). If correctly assigned here - sister to the extant representatives of the family (Ickert-Bond et al. 2005, 2007) - it is yet another fossil with interestingly plesiomorphous features (see also Calycanthaceae, Platanaceae, Fagaceae, etc.).
Evolution. Divergence & Distribution. Ickert-Bond and Wen (2006) give dates for divergence of clades within Altingiaceae; the basal split in the family is between the European + American and East Asian clades.
Chemistry, Morphology, etc. Secretory canals are also reported from Mytilaria (Hamamelidaceae s. str.). There are strongly vascularized structures ("phyllomes") interior to the staminal whorl; these may be staminodia, nectaries or organs sui generis. The orientation of the carpels varies (Bogle 1986). For the interpretation of the knobs, etc., surrounding the carpellate flowers, see Ickert-Bond et al. (2005). This and Hamamelidaceae - "micropyle faces upwards"?
Endocarpial cells are thickened and elongated transverse to the long axis of the fruit, and they look almost palisade in transverse section. The testa is notably thinner than that of most Hamamelidaceae. Ickert-Bond et al. (2005) suggest that in Liquidambar the exotegmen "constitutes most of the seed coat", although it is absent in most Hamamelidaceae, a point also made by others (e.g. Mohana Rao 1974). This is not immediately evident in the sections presented (e.g. Fig. 9, G-J) nor in Melikian (1973) and Z.-Y. Zhang and Wen (1996), but if confirmed (see e.g. Ickert-Bond et al. 2007) it will be another sharp difference from the more or less massively mesotestal seeds of most Hamamelidaceae.
For information about Hamamelidaceae s.l., see Bogle (1986: floral morphology, etc.), Ferguson (1989: general, esp. fossils), Skvortsova (1960: petiole), Melikian (1973: seed coat anatomy), Zavada and Dilcher (1986: pollen), and Endress (1993: general).
Phylogeny. Shi et al. (2001) present a molecular phylogeny of Altingiaceae, and this suggests that there is only one genus, in contrast to morphological phylogenies (Ickert-Bond et al. 2005, 2007).
Classification. It is best that a single genus be recognised, both because of phylogeny (e.g. Ickert-Bond & Wen 2006) and because species of the two genera that have been recognized, Liquidambar and Altingia, can hybridize (Wu et al. 2010).
Previous Relationships. Altingiaceae have often been included in Hamamelidaceae (e.g. Cronquist 1981).
[Hamamelidaceae [Cercidiphyllaceae + Daphniphyllaceae]]: ?
HAMAMELIDACEAE R. Brown, nom. cons. Back to Saxifragales
Trees or shrubs, evergreen; (C-glycosylflavones +); (vestured pits +; true tracheids +); sclereids common; petiole bundle (±) annular (with adaxial bundle; arcuate); stomata often paracytic, but variable, inc. laterocytic; hairs stellate (other); leaves two-ranked (opposite, spiral), lamina vernation ± conduplicate-flat or -plicate, (margins entire), stipules cauline; flowers (2-)4-5(-7)-merous; K free to connate; A = and opposite sepals (3-many); staminodia opposite petals, anthers with two pairs of valves, often basifixed, (connective not prolonged); pollen tricolpate, (6-rugate); nectary ± annular, staminodial, or on base of C [last two the same?]; G , styluli ± long, stigmas with multicellular protrusions, but no papillae; ovules ca 6/carpel, often epitropous, outer integument 6-12 cells across, inner integument 2-3 cells across, (micropyle zig-zag), hypostase +; fruit a loculicidal and septicidal capsule, K often persistent; hilum large, coat often with often discoloration near the hilum, testa thick, hard, multiplicative, exotestal cells thickened (not), mesotesta massive, usually of ± fibrous sclerotic cells, tegmen tanniniferous; endosperm slight, perisperm +, (polyembryony +).
27[list]/82 - four groups below. Tropical to temperate, esp. East Asia to Australia, not South America (map: from Vester 1940; Vink 1957; Ying et al. 1993; Fl. N. Am. 3, 1997; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003; Coates Palgrave 2002). [Photos - Collection] [Photo - Flower]
Age. An estimate of the crown-group age of Hamamelidaceae is a mere (42-)27, 25(-13) m.y. (Bell et al. 2010) or a very different (110-)104, 87(-81) m.y. (Wikström et al. 2001), but both these ages are in the context of relationships in the order that are very different from those above.
1. Exbucklandoideae Harms
(Venation pinnate), (stipules 0); inflorescence capitate; (C 0); G half inferior, (styluli long); (ovules to 20/carpel); outer integument ca 2 cells across [Exbucklandia]; exotestal cells alone thickened; n = 12, 16.
2/ca 7. East Himalayas and South China to Sumatra.
Synonymy: Exbucklandiaceae Reveal & Doweld, Rhodoleiaceae Nakai
[Mytilarioideae [Disanthoideae + Hamamelidoideae]]: seeds not winged.
2. Mytilarioideae H. D. Chang
(Secretory canals +); nodes 5:5; (stipule 1, tubular - Chunia); (K 0, C 0 - Chunia); (C and A basally fused, forming a tube); G ± inferior; ovules 2/carpel; n = ?
2/2. Kwangsi, Laos, Hainan.
[Disanthoideae + Hamamelidoideae]: C ribbon-like, adaxially circinate.
Age.The age of this node is estimated at (92-)84, 61(-53) m.y. (Wikström et al. 2001).
3. Disanthoideae Harms
Plant deciduous; flowers paired; nectary at base of C; anthers with slits; G superior, styluli short, stout; n = 8.
1/1: Disanthus cercidifolius. E. China, Japan.
Synonymy: Disanthaceae Nakai
4. Hamamelidoideae Burnett
Plant evergreen or deciduous; (stomata anomocytic); (buds naked), (perula 1), prophyll 1 (2), basal, then an internode; lamina with pinnate/craspedodromous venation, vernation conduplicate-plicate; inflorescence racemose, spicate, (with 3-flowered lateral cymes); (K [5-9]); (C not circinate), (0); A -23, centripetal or centrifugal, anthers with 1 or 2 pairs of valves, or slits; tapetum multinucleate; G superior to inferior; (styluli long); ovules 1/carpel (-3, 2 sterile), (apotropous), parietal tissue 8-10 cells across, (nucellar cap ca 2 cells across); fruit with ballistic dispersal of seeds; (endosperm cellular - Parrotiopsis); n = 12.
23/78. Tropical to temperate, esp. East Asia to Australia, not South America.
Synonymy: Fothergillaceae Nuttall, Parrotiaceae Horaninow
Evolution. Divergence & Distribution. Allonia decandra, a fossil probably to be placed in crown-group Loropetalineae, was collected from ca 83 m.y.o. rocks of the Cretaceous-Campanian in the eastern U.S.A., it has twice as many stamens as petals and a lobed disc adaxial to them (Magallón-Puebla et al. 1996); the seeds are rather angled, so there may have been more than one per loculus. For the early Tertiary fossil history of what are now East Asian endemic members of the family, see Manchester et al. (2009).
For the evolution of the flower in Hamamelidoideae, see Magallón (2007; fossils included, optimisation on to more than one topology).
Pollination Biology. There is considerable variation in floral morphology. Corylopsis has rather ordinary-looking flowers with obovate petals, although they are probably derived. In Parrotiopsis there are showy inflorescence bracts, and these are bright red in Rhodoleia, and there the whole inflorescence is very like the flower of, say, Calycanthaceae. Petals may be lost, as in Fothergilla where the inflorescence is made conspicuous by the plump and showy white filaments (see Endress 1978 for a discussion of the floral morphology of those Hamamelidaceae without a perianth). Eustigma has quite long white styluli and massive, purplish stigmas that are the most conspicuous parts of the flower.
Fertilization in Hamamelidaceae is often much delayed.
Plant-Animal Interactions. For the phylogeny of hormoraphidine aphids, notable gallers on Hamamelidoideae with ca 13 genera of aphids known from Distylium alone, see J. Chen et al. (2014).
Chemistry, Morphology, etc. What is going on with the growth of Exbucklandia? There is variation in the direction of initiation of the stamens in multistaminate androecia (Endress 1976); it can be centripetal (Matudaea) or centrifugal (Fothergilla). Exbucklandia is reported to have a remarkably long outer integument, although it is developed only on one side of the micropyle (Kaul & Kapil 1974).
Much additional information can be found in Endress's early work (1967a [general, comparison with Betulaceae, Corylopsis is the link], 1970 [inflorescence], 1971 [inflorescence, flower], 1976, [floral development], 1993 [general]). For petiole anatomy, see Skvortsova (1960), for embryology, see Kapil and Kaul (1974: Parrotiopsis); for seed anatomy, see Mohana Rao (1974), Z.-Y. Zhang and Wen (1996), and Benedict et al. (2008: also fruits and fossils), and Magállon et al. (2001 and references) and Zhao and Li (2008) for fossils.
Phylogeny. A clade including Exbucklandioideae and Mytilarioideae was apparent only in the analysis of ITS data and good sampling (75% bootstrap, better if gaps scored as a fifth character state: Li et al. 1999b; c.f. Shi et al. 1998); the genera included have in the past been placed in three subfamilies. With rbcL data, Mytilaria alone was rather weakly supported as sister to [Disanthoideae + Hamamelidoideae] (Li et al. 1999a). However, a later two-gene analysis resulted in strong support for the clades represented by the four subfamilies above and their relationships (Li 2008).
Within Hamamelidoideae [Corylopsideae (monotypic) + Loropetaleae (weak support)] were sister to the rest, but tribal interrelationships had for the most part only weak support (Li & Bogle 2001; Li 2008). See Xie et al. (2010) for the phylogeny and biogeography of Hamamelis.
Classification. For a classification of Hamamelidoideae, see Li and Bogle (2001).
[Cercidiphyllaceae + Daphniphyllaceae]: plant dioecious; flowers small, C 0; staminate flowers: , filemants at most barely longer than anthers; carpellate flowers: ovary superior; endosperm cellular.
Chemistry, Morphology, etc. The filaments are at most only slightly longer than the anthers, quite common in wind-pollinated flowers.
CERCIDIPHYLLACEAE Engler, nom. cons. Back to Saxifragales
Deciduous trees, with short shoots; chalcones, dihydrochalcones +; cork in outer cortex; primary stem with continuous cylinder; prophyll adaxial; leaves usu. opposite, lamina vernation involute, (margins entire), stipule adaxial-petiolar; inflorescence capitate; P 0, floral apex?; staminate "flower": A 16-34 [= several flowers], anthers long; pollen tricolpate; carpellate flower: G free, single, suture appearing to be abaxial, ["1-8", = as many flowers, each subtended by a bract], styluli long, stigmas decurrent their entire length; ovules many/carpel, outer integument 4-5 cells across, inner integument 2-3 cells across; fruit a follicle; chalazal appendage with hair-pin loop vascular bundle; testa undistinguished, exotestal cells enlarged, slightly thickened, tegmen tanniniferous; endosperm slight, suspensor single-celled, cell notably enlarged; n = 19.
1[list]/2. China and Japan (map: from Heywood 1978; Fu & Hong 2000). [Photos - Collection.]
Evolution. Divergence & Distribution. For the early Tertiary fossil history of Cercidiphyllum, see Manchester et al. (2009). Qi et al. (2012) found substantial genome structure in populations of Cercidiphyllum, which is by no means a relict.
Palaeocene fossils (Joffrea) have 2-carpellate flowers borne on an elongated axis with the adaxial sutures of the carpels facing each other (Crane & Stockey 1985, 1986). The "flowers" of today's species can be interpreted as pseudanthia. Each carpel represents a carpellate flower, indeed, the carpels are sometimes slightly separated from one another on the stout green axis, that of the "pedicel"=inflorescence. Both individual carpels and groups of stamens are subtended by bracts and are more or less decussately arranged. Yan et al. (2007) suggest that the bract is "really" a tepal because it is developmentally so different from the vegetative leaves, although it may have teeth or be almost bilobed. However, it is most likely that the structure is a bract, and that the suture of the carpel is adaxial with respect to the floral axis that originally bore it.
Chemistry, Morphology, etc. Takhtajan (1997) described the venation of leaves on the long shoots as being pinnate, but the main secondary veins all arise within 5(-10) mm of the base.
Krassilov and Lowen (2007) thought that the flower of Cercidiphyllum was unlike that of other Saxifragales (see also Maskova 2010). Soltis et al. (2005: fig. 6:11) suggest perhaps inadvertently that the gynoecium is partly inferior.
For variation in nodal anatomy between leaves on long and short shoots, see Howard (1979), and for general information, see Endress (1993) and Crane and Du Val (2013).
DAPHNIPHYLLACEAE Müller Argoviensis, nom. cons. Back to Saxifragales
Evergreen trees or shrubs; plants Al-accumulators, route I iridoids, triterpene [squalene] alkaloids +, myricetin, hydrolysable tannins 0; pits bordered; true tracheids +; pith at least sometimes septate; pericyclic fibres 0; stomata paracytic (laterocytic, anomocytic); plant glabrous; leaves ± pseudoverticillate, spiral, lamina vernation ± flat, margins entire, secondary veins pinnate, stipules 0; flowers pedicellate; P +, uniseriate, ± sepal-like, 2-6 (0); staminate flowers: A 5-12(-24), anthers with slits, basal pit indictinct, filaments with 3 traces, (staminodes +); pistillode 0; carpellate flowers: P free or connate, or 0; staminodes 0/+; G [2(-4)], placentation apical-axile to parietal, styluli short, recurved, stigmas rather massive, with multicellular protrusions but no papillae; ovules (1)2/carpel, ± apical, pendulous, micropyle exostomal/zig-zag?, outer integument 3-6 cells across, inner integument 4-5 cells across, hypostase +; fruit a 1-seeded drupe; seeds not winged, seed coat persistent but thin-walled and crushed, or endotegmen tanniniferous, walls thickened; perisperm slight, embryo short, cotyledons same width as radicle, (polyembryony +); n = 16.
1[list]/10. East Asia to Malesia (map: from Huang 1997). [Photo - Fruit]
Evolution. Divergence & Distribution. It has been suggested that thhe flowers may be secondarily superior (D. Soltis et al. 2003b).
Plant-Animal Interactions. Some epiplemine Uraniidae (moths) have caterpillars that eat Daphniphyllaceae - and assorted asterids - probably because of the iridoids they have in common (Lees & Smith 1991).
Chemistry, Morphology, etc. Bhatnagar and Kapil (1982) described the endotegmic cells as being thickened and variously cutinised or sclerotic.
For general information, see Z.-Y. Zhang and Lu (1989) and especially Kubitzki (2006b), for information on stomata, etc, see Tang et al. (2009); for a monograph, see Huang (1965).
Previous Relationships. Daphniphyllaceae have been difficult to place, sometimes being associated with Euphorbiaceae, etc., or placed in a separate order in the Hamamelidae (Cronquist 1981). Balanopaceae (see Malpighiales) were included in a bigeneric Daphniphyllanae by Takhtajan (1997).
[[Crassulaceae [Aphanopetalaceae [Tetracarpaeaceae [Penthoraceae + Haloragaceae]]]] [Iteaceae [Grossulariaceae + Saxifragaceae]]]: vessel elements with simple perforation plates; petiole bundle(s) arcuate; cuticle waxes not tubular; venation ± pinnate; ovules apotropous [all?]; K persistent, withered.
Age. The crown-group age of this clade is some (96-)91, 78(-73) m.y. (Wikström et al. 2001, 2004), (88-)80, 77(-69) m.y. (Bell et al. 2010), or (114-)96.8(-90.1) m.y. (Chen et al. 2014).
Chemistry, Morphology, etc. Mauritzon (1933) provides information on the ovules and endosperm development for many taxa in this clade.
[Crassulaceae [Aphanopetalaceae [Tetracarpaeaceae [Haloragaceae + Penthoraceae]]]]: stem with endodermis, lamina venation pinnate, stipules 0; inflorescence cymose; flowers 4-merous; endosperm cellular.
Age. The crown-group age of this clade is around (88-)80, 77(-69) m.y. (Bell et al. 2010), (82-)77, 69(-64) m.y.a. (Wikstöm et al. 2001), or (109.7-)94(-85.6) m.y. (Chen et al. 2014).
CRASSULACEAE Jaume Saint-Hilaire, nom. cons. Back to Saxifragales
Succulent herbs to soft-stemmed shrubs; mycorrhizae 0; crassulacean acid metabolism common; flavones, acylated flavonol glycosides, sugar reserve as sedoheptulose, non-hydrolysable tannins +, hydrolyzable tannins 0; red pigment common, even in roots; (cork cortical); young stem with separate bundles; (medullary bundles +); sieve tube plastids lacking starch grains and protein inclusions; xylem rayless; nodes also 1:1-3, 3:3, etc.; cuticle waxes very variable; stomata usu. anisocytic; leaves succulent, lamina vernation flat to curved, margins entire, hydathodes +; inflorescence cymose; anthers median sagittate, latrorse; nectaries ± finger-like, at bases of carpels [ougrowths of carpels]; G ± free, opposite petals, with 5 vascular bundles, (placentation parietal), stigmas punctate to moderately capitate, (wet); ovules 1-many/carpel, micropyle bi- (exo-, endo-)stomal, outer integument ca 2 cells across, inner integument 2-3 cells across, nucellar cap ca 4 cells across, nucellar epidermal cells enlarged, apical cells ?tanniniferous, appearing subpalisade [for all, or Crassuloideae?], (conducting strand +); (megaspore mother cells several); fruit a follicle; exotestal cells with outer wall ± thickened, inner pigmented layer +; endosperm cellular and variants, (nuclear), chalazal haustorium +, embryo long, suspensor uniseriate, basal cell with mycelium-like haustorial branches; x = 8; germination epigeal and phanerocotylar.
34[list]/1400 - three subfamilies below. Cosmopolitan, esp. the Cape region and Mexico, but few in S. South America and the Antipodes, not in Polynesia, frequently in drier regions. (map: see Hultén 1958; Bywater & Wickens 1983; Jürgens 1995; Thiede 1994, 1995; Fl. China 8. 2001; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003). [Photo - Flower.]
Age. Diversification in this clade began (44-)41, 39(-36) m.y.a. (Wikstöm et al. 2001), while Bell et al. estimate an age of (63-)50, 47(-36) m.y. ago; around 45 m.y.a. is the estimate in J.-Q. Zhang et al. (2014b).
1. Crassuloideae Burnett
Leaves opposite, lamina with several marginal hydathodes only; flowers 3-9-merous; stamens = and opposite K, slightly introrse at anthesis; (G 3 - odd carpel abaxial - Tillaea); parietal tissue 1(-2) cells across, soon disappearing; follicles releasing seeds through apical pore; testa cells with sinuous anticlinal walls, unipapillate; first division of micropylar endosperm cell in horizontal plane; n = 7, 8.
2/196: Crassula (195). Esp. Southern Africa to S.W. Arabia, "Tillaea" more or less world-wide, the only representative of the family in the Antipodes.
Age. Around 33 m.y. is the estimate of the age of this clade in J.-Q. Zhang et al. (2014b: sampling).
Synonymy: Tillaeaceae Martynov
[Kalanchoideae + Sempervivoideae]: leaves spiral, lamina with single (sub)apical hydathode; A obdiplostemonous, introrse only in early bud; (placentae lobed); parietal tissue 1-4 cells across; seeds costate; first division of micropylar endosperm cell in vertical plane.
Evolution. Divergence & Distribution. The crown-group age of this clade is estimated at (49-)35, 33(-23) m.y. (Bell et al. 2010) and around 45 m.y.a. in J.-Q. Zhang et al. (2014b).
2. Kalanchoideae A. Berger
Plant ± woody; bufadienolides + [cardiac glycosides]; crystal sand +; (leaves opposite), (margins with teeth); flowers ?-merous; C connate; A with spherical connective prolongation; (styluli long); (central strand in nucellus); seeds 4-6-costate, with a micropylar corona; x = 9 [n = 9, 17 (18)].
4/200: Kalanchoe (145), Tylecodon (46). Old World, especially the Karroo in southern Africa, but extending to South East Asia and Malesia, not Australasia.
3. Sempervivoideae Arnott
(Pyrrolidine and piperidine alkaloids +, nonhydrolyzable tannins 0 - esp. Sedum acre group); (leaves opposite); flowers 4-32-merous; (C connate); (stamens = and opposite K); (infra-stylar extra-gynoecial compitum/pollen tube growth - Sedum); nucellus elongated, with central strand; (follicle with abaxial dehiscence - Diamorpha); seeds ³6-costate; suspensor with compound plasmodesmata; n = >5, much variation (up to n = 320 - Sedum suaveolens).
28/1005: Sedum (420), Echeveria (140), Rhodiola (90), Sempervivum (65), Dudleya (47). Largely N. hemisphere.
Synonymy: Cotyledonaceae Martynov, Rhodiolaceae Martynov, Sedaceae Roussel, Sempervivaceae Jussieu
Evolution. Divergence & Distribution. Aeonium, a largely Macaronesian genus with the most endemic species there, has striking growth forms, some arborescent, each of which seems to have evolved just once (Mes & t'Hart 1996).
The distinctive wood, which lacks rays and has very short vessel elements with annular and helical thickening, is probably paedomorphic (t'Hart & Koek-Noorman 1989); plant chemistry, in particular the presence of hydrolyzable tannins and the absence of non-hydrolyzable tannins, as in other woody Saxifragales, is consistent with this idea (Thiede & Eggli 2006).
There have been several origins of sympetaly in Sedoideae s.l. ('t Hart et al. 1999; Carrillo-Reyes et al. 2009); both it and epipetaly tend to be weak. The increase in numbers of flower parts in some Sedoideae - some have a multistaminate androecium - is in the context of an increased merousness of the whole flower; the relation between the number of parts of each whorl is like that of other basic core eudicot flowers (see also the euasterid clade), i.e. K = C = G; A = 2x C.
All ca 200 species of the Echeveria group (Sempervivoideae) appear to be interfertile, a remarkable situation apparently without parallel in flowering plants (Uhl 1992).
For suggestions as to the base chromosome numbers of the family and of its major clades, see Mort et al. (2001).
Ecology & Physiology. Members of the family are an important component of the vegetation of the winter rainfall Succulent Karoo of south west Africa (Ogburn & Edwards 2010).
Crassulacean acid metabolism (CAM) is common throughout the family (e.g. references in Winter & Smith 1996a). It has also been reported from aquatic species of Crassula (Keeley 1998). For CAM variation within Kalanchoe, see Gehrig et al. (2001) and Kluge and Brulfert (1996).
Some species of Kalanchoe produce plantlets in notches at the margin of the leaf blade; these have rather aptly been called foliar embryos (Yarborough 1932). Both embryogenetic and organogenetic pathways have been coopted, and the young plantlets have cotyledon-like first leaves; unlike seeds, plantlets show no dormancy, a gene that induces dormancy in Arabidopsis not being functional (Garcês et al. 2014). Species in which development of plantlets is constitutive, i.e. plantlets are produced without the plant being damaged, do not produce viable seed (Garcês et al. 2007).
Chemistry, Morphology, etc. Anthocyanin is also found in the roots of Saxifragaceae, as well as Melastomataceae, Balsaminaceae, Asteraceae, Droseraceae, and Francoaceae (Krach 1976; Molisch 1928). Sedoheptulose is the most abundant sugar in Crassulaceae; isocitrate is common, unlike in other succulents (Thiede & Eggli 2006). The sieve tube plastids are a distinctive variant, lacking starch, the S0 type (Behnke 1988a). For (mistaken) reports of cortical vascular bundles, see Thiede and Eggli (2006). The leaf blade usually lacks palisade tissue, and there are often stomata on both sides. The stomata may also be heliocytic, with an additional ring of distinct cells outside a basically anisocytic configuration.
There is sometimes only a single vascular trace to the calyx (t'Hart & Koek-Noorman 1989). Anthers early in development are introrse, but often at maturity the sporangia are equidistant from one another (Wassmer 1955). According to D. Soltis et al. (2003b), the ovary is secondarily superior. Although this seems unlikely, the very base of the ovary is sometimes inferior, and the carpels, apparently free, are slightly connate at the base; a small amount of axial tissue is also apparent in the gynoecial region of some taxa (Wassmer 1955, q.v. for gynoecial details). The nucellar epidermal cells seem to be large and more or less radially elongated in Crassuloideae (in particular) and Kalanchoideae; in some Sedoideae megaspores elongate - sometimes those from the same megaspore mother cell - and grow towards the micropyle, and there and in Kalanchoe two embryo sacs may develop (Mauritzon 1933: much information; Subramanyan 1968). Haustoria from places other than the massive suspensor are reported for Crassulaceae (Mickesell 1990). Distinctive compound plasmodesmata in the suspensor cell walls have been found in some Sempervivoideae, although their distribution within the family is unclear (Kozieradzka-Kiszkurno et al. 2011). The testal cells of Crassula often have a single papilla and sinuous anticlinal walls (e.g. Bywater & Wickens 1983). There is no tegmen. Spongberg (1977) notes that the endosperm is usually scanty, while Mabberley (1997) describes it as being copious; the former is correct.
For general recent accounts of the family, see Eggli (2003: enumeration of all species) and in particular Thiede and Eggli (2006); for chemistry, see Stevens (1995), for nodal anatomy, which is variable, see Jensen (1968), for floral development, see Nelson (1990), and for embryology, etc., see Rombach (1911), Vignon-Fétré (1968) and Subramanyam (1970).
Phylogeny. The basic phylogenetic structure of the family seems fairly well established (e.g. van Ham 1995; van Ham & 't Hart 1998; Mort et al. 2001, 2010 for a summary; Mayuzumi & Ohba 2004). The rather highly derived Crassuloideae are sister to the rest of the family; Kalanchoe and relatives are sister to the rest of Sedoideae (e.g. Mort et al. 2001; Mort 2002; Thiede & Eggli 2006).
Within Crassuloideae, Tillaea is polyphyletic and embedded within Crassula (Mort et al. 2009; Mort et al. 2010). For the phylogeny of Kalanchoe, see Gehrig et al. (2001) and Kluge and Brulfert (1996).
Sedum appears in five of the seven main clades apparent in phylogenetic analyses of Sempervivoideae (van Ham 1995; van Ham & 't Hart 1998; Mayuzumi & Ohba 2004). Within the Acre clade of Sedum, most New World Sedoideae as well as all the old Echeverioideae in the study formed a single clade, although it was only poorly supported (Carrillo-Reyes et al. 2009). For relationships of the Acre clade and other east Asian Sedoideae, see Mayuzumi and Ohba (2004). The limits of Graptopetalum are unclear, and there was little strong support along the backbone of the tree (Acevedo-Rosas et al. 2004). For relationships within Dudleya, probably monophyletic, see Yost et al. (2014), and for those within Rhodiola, see J.-Q. Zhang et al. (2014a, b).
Classification. Within Sempervivoideae, generic limits are unclear (an understatement), and many genera, some previously placed in what were considered to be different subfamilies, e.g. Sedoideae and Echeverioideae, hybridise (e.g. Uhl 1976; 't Hart et al. 1999). Thiede and Eggli (2006) provide a guide through the chaos; , and although they prefer to retain a paraphyletic Sedum, this wil have to be dismembered or its circumscription much enlarged. For Kalachoe, see Descoings (2006).
Previous Relationships. Crassulaceae have been linked with Rosaceae and Podostemaceae because of embryological similarities... (Rombach 1911).
[Aphanopetalaceae [Tetracarpaeaceae [Penthoraceae + Haloragaceae]]]: ?nodes 1:1; fruit indehiscent.
Age. The age for this node is estimated to be (92-)82.5(-75.7) m.y. (Chen et al. 2014).
APHANOPETALACEAE Doweld Back to Saxifragales
Scrambling shrub; chemistry?; vessel elements with scalariform perforation plates; pericyclic fibres 0; petiole with 3 (1) bundles; leaves opposite, teeth with a single vein and a distinct dark apex, stipules +, looking like teeth; inflorescence axillary, cymose or flowers solitary; hypanthium short; K large, petal-like, C 0 [rudiments visible only when very young]; pollen with rugulate-stellate surface; G seminferior, opposite petals, style single, with four canals, branches short; ovule 1/carpel, apical, pendulous, apotropous, micropyle bistomal, outer integument ca 8 cells across, inner integument ca 2 cells across, parietal tissue ca 4 cells across; archesporium multicellular; fruit a nut, K enlarging; seed 1; seed coat?; endosperm development?, embryo curved, size?; n = ?
1/2. W. and E. Australia (map: from Australia's Virtual Herbarium [outliers omitted] i.2014). [Photo - Flower.]
Age. The two species may have diverged (19.6-)11(-4.7) m.y.a. (Chen et al. 2014).
Chemistry, Morphology, etc. The ray parenchyma stores starch. Two small bundles soon diverge from the main leaf trace. It is unclear if the stipules "are" stipules or colleters (Kubitzki 2006b).
As in Saxifragaceae and Iteaceae, the vascular trace in the petal plane gives a branch to the lateral sepal position, also carpel wall and lateral carpel traces and a single stamen trace; the trace in the sepal plane supplies the carpel wall and median carpel bundle and provides a stamen bundle.
Some information is taken from Kubitzki (2006b: general), Jensen (1968: vascular system), Dickison (1980b: nodal anatomy), Dickison et al. (1994: anatomy), Bensel and Palser (1975b: floral anatomy), and Mauritzon (1939a: embryology).
Previous Relationships. Aphanopetalum used to be included in Cunoniaceae (Cronquist 1981), latterly as a separate subfamily (Takhtajan 1997).
[Tetracarpaeaceae [Penthoraceae + Haloragaceae]]: ?
Age. The age of this node is some (72-)61, 58(-46) m.y. (Bell et al. 2010), (62-)58, 53(-49) m.y. (Wikström et al. 2001), or (85.3-)78.1(-72.9) m.y. (Chen et al. 2014).
Classification. Although combination of these three rather small families was an option in A.P.G. II (2003), there seems to be little or nothing holding them together morphologically (see also Moody & Les 2007) and they are kept separate in A.P.G. III (2009).
TETRACARPAEACEAE Nakai Back to Saxifragales
Evergreen shrub; chemistry?; plant glabrous; leaves spiral, petiole short; inflorescence terminal, racemose; (flowers 5-merous), floral apex convex; C spatulate; A 4-8, basal pits?, fibrous endothecium 0; nectary 0; G free, 4 (5), opposite petals, style short, stigma not expanded; ovules many/carpel, micropyle exostomal, parietal tissue ca 4 cells across; fruit a follicle; exotestal cells ± elongated longitudinally, outer walls thickened, no mechanical layer; embryo small; n = ?
1/1: Tetracarpaea tasmannica. Australia, Tasmania only. [Photo - Habit.]
Chemistry, Morphology, etc. The lamina teeth are perhaps hydathodal, but there are no water pores. The ovary is apparently secondarily superior (D. Soltis et al. 2003b).
See Kubitzki (2006b: general), Hils et al. (1988: anatomy) and Mauritzon (1933: ovules) for information.
Previous Relationships. Tetracarpaea used to be included in Grossulariaceae (Cronquist 1981), i.e., it was a woody saxifrage.
[Penthoraceae + Haloragaceae]: ± herbaceous; embryo long.
Age. The age of this node is estimated at (63-)51, 48(-35) m.y. (Bell et al. 2010), (51-)47, 43(-39) m.y. (Wikström et al. 2001), or (74.4-)71.3(-70.1) m.y. (Chen et al. 2014).
PENTHORACEAE Britton, nom. cons. Back to Saxifragales
Rhizomatous herbs; flavonoids +, flavones, myricetin, non-hydrolysable tannins 0; cork ?; young stem with pseudosiphonostele; endodermoid layer?; pericyclic fibers 0; leaves spiral, lamina amphistomatic, vernation supervolute, teeth hydathodal, colleters +; inflorescence terminal, cymose; flowers 5-7-merous, hypanthium +; C 0(-7); A 2x K, lacking a basal pit, latrorse; pollen oblate; G [5-8], half inferior, opposite sepals, apical parts free, becoming superior, placentae intrusive, styluli submarginal, stigmas capitate; ovules many/carpel, micropyle?, funicles long; free part of each carpel basally circumscissile in fruit; exotestal cells with outer wall ± thickened, papillate, micropylar operculum endostomal, tegmen otherwise crushed; first endosperm division very asymmetrical, cell at end of suspensor large; n = 8 (9).
1[list]/2. East and South East Asia, E. North America (map: from Hong 1993; Fl. China 8. 2001). [Photo - Penthorum Inflorescence.]
Age. Crown-group Penthoraceae are only 6.5-2.4 m.y.o. (Thiede 2006 for references) or (5.8-)2.9(-1) m.y.a. (L.-Y. Chen et al. 2014).
Evolution. Divergence & Distribution. The E. North American/East Asian disjunction is dated to a mere 6.5-2.4 m.y.a. (Thiede 2006 for references).
Chemistry, Morphology, etc. Cork in the root is initiated in a superficial position (van Tieghem 1899).
The sepals are unequal in size and the bracts are lateral to the pedicels. There is a much-enlarged but non-dividing micropylar cell in the embryo suspensor - c.f. Haloragaceae and their haustorial suspensor. Danilova (1996) shows the carpels as opposite to the calyx. The first two pairs of seedling leaves are opposite.
See Spongberg (1972, in Saxifragaceae) and Thiede (2006), both general, Haskins and Hayden (1987) and Gornall (1998: as Saxifragaceae), both anatomy, Mauritzon (1933: endosperm), and Nemirovich-Danchenko (1994b: seeds) for information.
Previous Relationships. Penthorum used to be included in Saxifragaceae (Cronquist 1981).
HALORAGACEAE R. Brown, nom. cons. Back to Saxifragales
Flavones +, flavonols 0; cork ?; often calcium oxalate crystals in hair-like cortical cells; cuticle waxes 0 (parallel platelets); leaves opposite (spiral), (pinnately compound), lamina vernation conduplicate-flat, colleters +?; inflorescence ± determinate, (branches dichasial), fasciculate, or flowers solitary; flowers small [petals <4 mm long], 4-merous; K valvate, C deciduous; A 8, (= and opposite sepals), anthers much longer than filaments, (apiculate), basal pits?; pollen grains tricellular, 4-6 colpate; ovary inferior, (sub 1-locular), opposite petals or odd member adaxial, styluli with swollen bases, stigmas (sessile), capitate or not, penicillate, dry; ovule 1/carpel [fertile], apical, pendulous, apo(epi-)tropous, outer integument 2-3 cells across, inner integument ca 2 cells across, parietal tissue 2-3 cells across, nucellar cap +/0, postament +, poorly developed funicular obturator +; embryo sac with antipodal cells persistent; fruit nut-like, indehiscent, exocarp often ornamented; exotesta (and hypodermal layer) persistent, thin-walled, rest obliterated; endosperm starchy, (nuclear), haustorial suspensor +, (embryo short), cotyledons rather short.
9[list]/145 - two groups below. World-wide, but especially Australia.
Age. Crown-group Haloragaceae are estimated to be (56.3-)47.1(-37.3) m.y. (Chen et al. 2014).
1. Haloragodendron + Glischryocaron
Herbs with woody rootstock to small trees; flowers perfect; (petals to 4 cm long); pollen apertures crassimarginate; fruit winged, 1-seeded; n = 7.
2/9. Southern and Western Australia.
Age. The crown-group age of this clade may be some (14.8-)10.3(-6.4) m.y. (Chen et al. 2014).
2. Myriophylleae Reichenbach
Aquatic (ephemeral) herbs to shrubs; plant monoecious (dioecious), (flowers perfect); C (0), (hooded); pollen 4-6(-20)-aperturate, (porate), apertures tenuimarginate; (ovules 2/carpel); fruit 1-4-seeded, (schizocarp); n = 6, 7 (8).
7/136: Myriophyllum (60), Gonocarpus (41), Haloragis (28). Tropical South America (map: from van Steenis 1962; Hultén 1958, 1971; van der Meijden 1971; Wood 1972; Orchard 1981; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003; Chen et al. 2014). [Photo - Collection.]
Age. The crown-group age of this clade is estimated to be (50.9-)42(-33.5) m.y. (Chen et al. 2014).
Synonymy: Cercodiaceae Jussieu, Myriophyllaceae Schultz-Schultzenstein
Hernández-Castillo and Cevallos-Ferriz (1999) suggest that the fossil Tarahumara sophiae (found in Mexico in deposits laid down ca 70 m.y.a.) had carpels free from one another but adnate to a hypanthial wall (c.f. some Rosaceae-Spiraeaoideae-Pyrinae), while its fruit is described as being drupe-like. Although perhaps assignable to this part of the tree, its morphology is unlike that of any extant member of Haloragaceae.
Evolution. Divergence & Distribution. The family may have an Australian origin (e.g. Moody & Les 2007), and there has since been substantial dispersal, especially of the aquatic taxa - probably because of bird dispersal (L.-Y. Chen et al. 2014, q.v. for more details and dates).
Fossil Proserpinaca is common in Europe and Asia, but the genus is now restricted to the New World, where it is scattered (Chen et al. 2014: Fig. 1).
Ecology & Physiology. The aquatic habit evolved at least twice in the family (L.-Y. Chen et al. 2014).
Pollination Biology. In some species of Haloragodendron the whole inflorescence is coloured.
Chemistry, Morphology, etc. Nodal anatomy was observed in Haloragis erecta and Laurembergia, vernation in the first. Pelargonidin occurs in leaves, as in Saxifragaceae (Doyle & Sogin 1988). Adventitious roots arise between the leaves in Haloragis.
Trihaloragis has flowers in which all whorls are trimerous, very unusual in eudicots; Moody and Les (2007) point out the extensive variation in floral merism in the family. Myriophyllum appears to have endostomal ovules (Batygina et al. 1985), while Bawa (1970) noted that the archesporial cell (= megaspore mother cell) was hypodermal, i.e. the ovule is tenuinucellate/there is no parietal tissue. Nijalingappa (1975) described the embryo sac of Haloragis micrantha as having a hypostase; there is definitely a postament. Corner (1976) described the endosperm as being starchy.
For general information, see Orchard (1975: Antipodean taxa, inc. much detail about floral anatomy, etc.), Orchard (1990; Australian taxa), and Kubitzki (2006b); for other information, see Orchard and Keighery (1993: Meziella) and Praglowski (1970: pollen).
Phylogeny. See Moody and Les (2001, 2004 and especially 2007, in the latter study nuclear ITS and chloroplast genes in some conflict) for relationships within the family. The woody [Glischrocaryon + Haloragodendron] clade is sister to other Haloragaceae (see also L.-Y. Chen et al. 2014), although the monophyly of the two genera themselves is not certain. The rest of the family forms a single clade, but relationships within it are uncertain, Meionectes and Proserpinaca in particular not having well-supported positions (Moody & Les 2007); the latter two genera are sister taxa, the combined clade being sister to the remainder (L.-Y. Chen et al. 2014). The trimerous Trihaloragis is sister to all other members of this clade (Moody & Les 2007). For the phylogeny of Haloraghis (and the disappearance of Meziella) see Moody and Les (2009).
Previous Relationships. The monotypic Haloragales were placed near Saxifragales by Takhtajan (1997) or linked with Gunneraceae and placed next to Myrtales, as by Cronquist (1981). Historically Gunneraceae and Haloragaceae q.v. have often been associated, although their pollen is quite different (e.g. Praglowski 1970), the perianth of Gunneraceae is not differentiated into two whorls of sepals and petals, etc..
[Iteaceae [Grossulariaceae + Saxifragaceae]]: (vessel elements with scalariform perforation plates); leaves spiral; hypanthium +; stamens = and opposite K; ovules many/carpel; fruit a septicidal capsule.
Age. The age of this node may be (86-)81, 73(-68)) m.y. (Wikström et al. 2001: c.f. topology).
ITEACEAE J. Agardh, nom. cons. Back to Saxifragales
C-glycosylflavones +; placentation axile, micropyle?, style well developed; endosperm slight, ?type.
2/21. Rather scattered, warm temperate to tropical.
Age. The age of crown Iteaceae is (51-)46, 39(-34) m.y. (Wikström et al. 2001).
1. Pterostemon Schauer
Shrubs; ?chemistry; hairs glandular, conical to peltate; stipules cauline, minute; inflorescence a corymbose cyme; bracteoles 0, hypanthium?, K valvate; filaments flattened, toothed, anthers with basal pits?, staminodes 5, opposite petals; nectary 0; G , largely inferior, orientation?, (styluli ± radiating), stigma capitate, ?type; ovules 4-6/carpel, ascending, apotropous, parietal tissue ca 8 cells across; C also persistent in fruit; seed coat "cartilaginous"; n = ?
1[list]/3. Mexico (map: from Smith et al. 2004).
Synonymy: Pterostemonaceae Small, nom. cons.
2. Itea L.
Trees to shrubs; allitol +, flavonols, ellagic acid 0; hairs unicellular; young stem with separate bundles; pith chambered; lamina vernation conduplicate, margins spiny- or gland-toothed, stipules small, on petiole base or adjacent stem; inflorescence axillary, (branched) racemose; flowers rather small; C valvate; anthers lacking basal pits, connective protrusion apical, globular; pollen bilateral, 2-porate, ektexine homogeneous; nectary annular, at base of hypanthium; G  to subinferior, styles postgenitally fused at least at the stigma, stigma punctate-lobed, wet; parietal tissue 3-4(?-7) cells across; exotestal cells with outer walls thickened; (endosperm moderate - Itea rhamnoides), embryo incumbent; n = 11.
1[list]/18. South East Asia to W. Malesia, E. North America, E. and S. Africa (map: from Mai 1985; Aubréville 1974a; Coates Palgrave 2002; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003). [Photo - Itea Flower.]
Age. The fossil Divisestylus, from the late Cretaceous some 90 m.y. before present and perhaps part of the Itea clade, has five stamens opposite the sepals and ovaries and stigmas fused, but there are separate styles - just like Itea. However, the pollen is tricolpate and striate, suggesting that the the fossil is stem-group Itea (Hermsen et al. 2003).
Evolution. Divergence & Distribution. The distinctive pollen of Itea is known fossil in Europe in the Eocene and somewhat later in North America (Hermsen et al. 2003); fossils in western North America have been dated to 59-42 m.y., although there is some uncertainty here, or ca 3.7 m.y. in Western Europe (Hermsen 2013).
Chemistry, Morphology, etc. For the chemistry of Itea, see Bohm et al. (1999). Pterostemon also has flavones, in this being like other Saxifragales. Choristylis (= Itea) lacks axial parenchyma.
The ovule of Itea is sometimes described as being unitegmic, with the integument 6-7 cells across, but this appears to be incorrect (Kubitzki 2006b). Although the carpels are free initially, they become connate, even along the style (Ge et al. 2002), so perhaps the styles are more accurately described as being postgenitally connate styluli.
For additional information, see Spongberg (1972), Gornall et al. (1998) and Kubitzki (2006b), all general, Ramamonjiarisoa (1980: anatomy), Mauritzon (1933: ovules), and Bensel and Palser (1975b) and Ge et al. (2002), floral anatomy and development.
The pericyclic fibres of Pterostemon seem to be weakly developed and the androecium is obdiplostemonous. Similar peltate glandular hairs are known from Grossulariaceae.
For more information, see Goldberg (1986), Wilkinson (1994, 1998) and especially Kubitzki (2006b: as Pterostemonaceae), but Pterostemon is not well known.
Classification. Combination of Iteaceae and Pterostemonaceae was optional (as Iteaceae s.l.), see A.P.G. II (2003); this broadened circumscription was formally adopted by A.P.G. III (2009).
[Grossulariaceae + Saxifragaceae]: glandular hairs +; secondary veins palmate; G [2-3]; parietal tissue 3-6 cells across, (postament +); endosperm ± cellular, first diuvision asymmetrical [chalazal chamber small],, (micropylar chamber nuclear); germination epigeal, cotyledons expanded.
Chemistry, Morphology, etc. For endosperm development, see Gaümann (1919) and Dahlgren (1930).
GROSSULARIACEAE de Candolle, nom. cons. Back to Saxifragales
Shrubs; cork cambium outer cortical/pericyclic; underground stems with endodermis; pericyclic fibres 0; axial parenchyma 0; petiole bundles ± connate; lamina vernation conduplicate-plicate, margins also lobed, some teeth hydathodal, leaf base broad and with thin margins, (paired prickles at the nodes); inflorescence axillary, leafy below, racemose; pedicels articulated, bracteole single; (flowers 4-merous), hypanthium forming an obvious tube, nectary at base, C small, open, (staminodes +), (A 10), tapetal cells binucleate; pollen 5-15-porate, with distinctively rugose ectoapertures, tectum complete; ovary inferior, carpels usu. superposed, placentation parietal, style single, long, stigma capitate, wet; ovules with exostomal micropyle, outer integument 3-5 cells across, inner integument ca 2 cells across, parietal tissue ca 3 cells across, nucellar cap 0, postament +, hypostase +; fruit baccate; seeds hard, arillate, exotestal cells palisade, mucilaginous, all told this layer 3-6 cells across, endotestal cells crystalliferous, radial and inner walls lignified, ?tegmen cells elongated, tanniniferous; endosperm hemicellulosic, embryo short to long, cotyledons accumbent; n = 8, chromosomes 1.5-2.5 µm long.
1[list]/150: Ribes. Temperate N. hemisphere, also along the Andes (map: from Hultén 1968; Hultén & Fries 1986; Jalas et al. 1999; Fl. China 8. 2001; Malyschev & Peschkova 2004). [Photos - Collection.]
Evolution. Plant-Animal Interactions. The fruits of Ribes are an important food for Andean frugivorous birds. Several species of insects have been recorded as eating species of Ribes (Weigend 2006).
Bacterial/Fungal Associations. A number of fungi, including the ecomonically very important white pine blister rust (the basidiomycete Cronartium ribicola), spend part of their life cycle on the plants of this genus. In some places in North America attempts - largely unsuccessful - have been made to eradicate Ribes so as to disrupt the life cycle of this damaging fungus, Ribes harbouring the telial stage.
Chemistry, Morphology, etc. Stem collenchyma is well developed. Nectar glands on the anthers are reported from some species. There is considerable variation in pollen morphology, and Ribes divaricatum has pentacolpo-di-orate pollen (Weigend 2006). The stylar bundles are ventral carpellar (Saxena 1969).
Additional information is taken from Weigend (2006: general account), Stern et al. (1970) and Cutler and Gregory (1998), both anatomy, Klopfer (1969a, 1973) and Gelius (1967), floral morphology, and Mauritzon (1933) and Shamrov (1998), ovule/embryology.
Phylogeny. Weigend et al. (2002) and Senters and Soltis (2003) suggest phylogenies for Ribes.
Previous Relationships. Grossulariaceae as circumscribed by Cronquist (1981) are very heterogeneous, and include genera now placed in Phyllonomaceae and Escalloniaceae (both campanulids), Montiniaceae, Tribelaceae (both lamiids), Tetracarpaeaceae, Iteaceae (including Pterostemonaceae), and Celastraceae (all rosids).
Synonymy: Ribesiaceae Marquis
SAXIFRAGACEAE Jussieu, nom. cons. Back to Saxifragales
Herbs, rhizomatous or stoloniferous, mycorrhizae 0 [?how common]; cork also pericyclic; young stem with separate bundles; nodes also 1:1, 1:2 and 3<:3<; petiole bundles also annular (with medullary or adaxial bundles); hairs (uni-)multiseriate with multicellular glandular head; leaves (opposite), lamina vernation variable, (margins entire), (secondary veins pinnate), (leaf base broad, sheathing), colleters +; inflorescence terminal; A 10; tapetal cells 2-4-nucleate; (pollen 2-3- colpate); nectary +, ± annular (0); G superior to inferior, (free), carpels with 5 bundles, apical parts quite often free, orientation variable, placentation parietal to axile, styluli ± long, adaxially channeled, stigmas spatulate to capitate, wet or dry; outer and inner integuments ca 2 cells across, parietal tissue 2-6 cells across, nucellar cap +/0, (hypostase +); fruit also a follicle; exotestal cells with outer wall (radial walls) ± thickened, variously ornamented, inner pigmented layer +, (endotegmen crystalliferous); (endosperm helobial), moderate, embryo medium (large), cotyledons incumbent; radicle with anthocyanin; n = (5-)7(+); chloroplast rpl2 intron 0.
Ca 33[list]/540 - two groups below. Mostly N. temperate and Arctic (S. temperate, some tropical mountains) (map: from Hultén 1958, 1971; Meusel et al. 1965; Fl. China 8. 2001; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003). [Photos - Collection]
Age. The age of crown-group Saxifragaceae may be (50-)38(-26) m.y. (Bell et al. 2010) or (59-)54, 49(-44) m.y. (Wikström et al. 2001).
Tylerianthus, in Late Cretaceous deposits from eastern North America of ca 90 m.y. age, has been linked with Saxifragaceae; it has nectaries on the upper part of the inferior ovary, five sepals, five stamens opposite the sepals that alternate with five long, linear staminodes (Gandolfo et al. 1998b: also compared with Hydrangeaceae).
1. Saxifragoideae Beilschmied
(Flowers obliquely monosymmetric); (C 0, A 5); (pollen grains tricellular).
1/370-500. Mostly Arctic and northern montane, Saxifraga magellanica grows along the Andes.
2. Heucheroideae Burnett
(Leaves palmately or ternately compound), (stipule adaxial, basal or sub-basal on petiole, persistent, or paired, cauline [Astilbe]); flowers (3-10)-merous; (hypanthium 0); K 0-10, (with a single trace - Astilbe), (C laciniate or toothed; 0-6); (A 3-15; obhaplostemonous - Chrysosplenium); pollen colpate, colporate, or 6-9-porate; nectary disc-like (0); G [(3-5)]; (integument single, 4-6 cells across - Darmera); (endotegmen thick-walled - Heuchera, Tolmeia).
Ca 30/2: Micranthes (70), Chrysosplenium (55), Heuchera (43). Mostly N. temperate, also tropical montane and Arctic.
Synonymy: Brachycaulaceae Panigrahi & Dikshit, Chrysospleniaceae Berchtold & J. Presl, Pectiantiaceae Rafinesque
Evolution. Pollination Biology & Seed Dispersal. The polyphyletic Mitella, along with a few other Saxifragaceae, is very largely pollinated by fungus gnats, and this association has evolved in parallel. Flowers of these species are often more or less broadly saucer-shaped and the petals have very narrow lobes (Okuyama et al. 2008). Cryptic species are being discovered in the fungus gnat-pollinated Mitella sect. Asimitellaria (Okuyama & Kato 2009).
The moth Greya (Prodoxidae), related to Tegeticula of yucca moth fame, is both a seed predator and pollinator of some Saxifragaceae (Segraves & Thompson 1999); this association is being studied in considerable detail, clarifying the diversification of both plant and pollinating seed parasite (Rich et al. 2008 and references). Other insects can also pollinate the flowers, and their number varies from year to year (Pellmyr & Thompson 1996). There is great - and unusual, at least in taxa with comparable floral biologies - variation in floral scent in Lithophragma, one of the saxifragaceous genera involved (Friberg et al. 2013). It has been suggested that the general lability of ovary position in the family (e.g. Klopfer 1972b) is connected to selection by such pollinators (Soltis & Hufford 2002); protected, i.e. inferior, ovaries will be favoured.
The seeds of a number of forest-dwelling Saxifragaceae are dispersed by rain, whether by a splash cup mechanism, as in Mitella, or by the seeds being thrown from the fruit as it moves violently after being hit by a drop of water, as in Heuchera.
Bacterial/Fungal Associations. Short-cycle Puccinia rusts (Uredinales, basidiomycetes) are frequently found on Saxifragaceae (Savile 1979a, b).
Genes & Genomes. Introgressive hybridisation in the Heuchera clade is extensive and there are various combinations of chloroplast and nuclear genomes, for example, the chloroplast genome of Tellima is also found in Mitella (e.g. Soltis et al. 1993).
In Saxifraga s. str. the diploid chromosome number varies from 12-ca 200, in Micranthes from 10-120.
Chemistry, Morphology, etc. The distribution of druses and acicular crystals is of systematic interest (Gornall 1987); only Saxifraga s.l. has been studied in detail. Over 50 vascular bundles may enter the petiole base in some taxa. Hydathodes are common.
Saxena (1973) suggested that the androecium of Saxifragaceae was not obdiplostemonous; from Gelius's (1967) description of androecial development, the relationship between the whorls can change during development. The stylar vascular supply is from dorsal and ventral carpellar bundles; the vascularization of the nectary is variable (Saxena 1973). In at least some species of Saxifraga, and in Astilbe and Rodgersia, the two carpels are oblique, but in the latter two this is associated with inverted floral orientation, the odd K being abaxial; many other taxa have superposed carpels (Eichler 1878; Engler 1930a; Eckert 1966). Variation in ovary position within the family is extreme, even occurring within genera and between the different morphs of heterostylous flowers (e.g. Kuzoff et al. 2001; Soltis & Hufford 2002). In Chrysosplenium one carpel is open, the other closed. There is great variation in endosperm development, Mauritzon (1933) describing some taxa as having helobial endosperm.
Some information is taken from Morf (1950) and Spongberg (1972), details of vegetative anatomy from Thouvenin (1890) and Gornall (1998), of embryology from Pace (1912), Mauritzon (1933: much detail), Vignon-Fétré (1968) and Gornall (1989), of floral morphology from Klopfer (e.g. 1968, 1970a, b, 1973) and Klopfer and Ziesing (1971), of seed morphology from Knapp (1998), and details of floral anatomy from Bensel and Palser (1975b). McGregor (2008) provides a useful and well-illustrated summary of the ornamentally important Micranthes and Saxifraga. Given the history of the circumscription of Saxifragaceae, early references commonly contain information about a diversity of other families.
Phylogeny. There are two major clades in Saxifragaceae. One includes Saxifraga s. str., largely arctic-alpine in distribution. The Heuchera clade includes the rest, including Micranthes, which used to be part of Saxifraga; most of the morphological variation in the family occurs here, and it is predominantly temperate in distribution (Soltis et al. 2001; Xiang et al. 2012; Prieto et al. 2013). The inflorescence of Saxifraga s. str. often has cauline bracts, however, that of Darmera is scapose, and there are pollen and testa surface differences between the two. For relationships in Heuchera, see Folk and Freudenstein (2014); Mitella is polyphyletic.
Classification. Generic limits in the Heuchera clade are unclear (Soltis et al. 1996, and refs.; Okuyama et al. 2008).
Previous Relationships. In the past, genera "intermediate" between what was thought to be a very variable Saxifragaceae and other families tended to be included in Saxifragaceae. It hs long been recognized that this was because the inclusion of more odd genera in Saxifragaceae would have little effect on the family description since there was already so much variation included in it (Pace 1912). However, if placed in the more homogeneous Crassulaceae, for example, such genera would greatly affect the description of that family and hence make it less discrete (e.g. Penthorum). Many tenuinucellate and unitegmic genera that used to be included in Saxifragaceae or Grossulariaceae have turned out to be entirely unrelated to each other. There was clearly a division between Saxifragaceae s. str. + Grossulariaceae s. str., with petals that remain very small for quite some time during development, and Hydrangeaceae (also classically placed in this area), with their relatively faster-developing petals, as is common in the asterids (Gelius 1967), and that flags a major separation. Of Saxifragaceae in the old sense, Parnassia is in Celastraceae-Celastrales (a conclusion in agreement with data from floral anatomy - e.g. Bensel & Palser 1975a, d), Francoaceae are in Geraniales, Vahlia is unplaced in the lamiids, but is perhaps to be included in Solanales, and so on. However, the unitegmic Darmera is properly to be retained in Saxifragaceae (e.g. Gornall 1989).
CYNOMORIACEAE Lindley, nom. cons. To Rosales for alternative position!
Echlorophyllous, root parasite; vessel elements?; cork?; stomata 0; plant glabrous; leaves spiral; plant monoecious; inflorescence clavate-capitate; bracts deltoid; flowers minute; P +, uniseriate, (1)4-5(-8), basally connate or not; staminate flowers: A 1, adnate to P; pollen colporate; suborbicular/cristate nectary-stylodium +; carpellate flowers: staminodia 0; G 1, inferior, style long, channeled; ovule 1/carpel, apical, pendulous, straight, unitegmic, integument 5-8 cells across, parietal tissue 1-2 cells across; fruit an achene; testa ca 7 cells across, persistent, exotesta slightly developed, walls little thickened; endosperm cellular, copious, thick-walled, embryo undifferentiated; n = 12, size strongly bimodal.
1[list]/2. Mediterranean to C. Asia (map: from Jalas & Suominen 1976; Jäger et al. 1985; Hansen 1986; Flora of China 13, 2007 [approx.]; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010). [Photo - Habit © D. L. Nickrent.]
Age. An age of (117-)100.2(-76) m.y. was suggested for the clade [Cynomoriaceae [Paeoniaceae + Altingiaceae]] in Naumann et al. (2013).
Evolution. Divergence & Distribution. In the Mediterranean area the hosts of Cynomoriaceae are often members of Cistaceae or Amaranthaceae, elsewhere Cynomorium parasitizes Amaranthaceae, Tamaricaceae, Nitrariaceae, etc. (Jäger at al. 1985).
Chemistry, Morphology, etc. The root has root hairs. The stem seems to develop inside a cavity in the tuber-like haustorial structure attached to the host (Solms-Laubach 1867).
Perfect flowers are also known. The perianth is less well developed in pistillate than in staminate flowers, and there is debate as to its morphological nature. The pistillode in staminate flowers may be superior or inferior, according to Hooker (1856), clearly a matter that should be cleared up. The channeled style has two vascular bundles, together a rather odd combination. It is unclear whether the parietal tissue is 1-2 cells across, or whether these cells represent a nucellar cap.
For general information, see the Parasitic Plants website (Nickrent 1998 onwards) and also Heide-Jørgensen (2008), for some chemistry, see references in Z.-H. Zhang et al. (2009), for details of seed anatomy, see Takhtajan (2000), for morphology, see Weddell (1860), and for ovule, etc., see Juel (1902: ?nucellar cap) and Teryokhin et al. (1975).
Previous relationships. Cynomoriaceae have usually been included in Balanophoraceae or Balanophoranae (e.g. Cronquist 1968; Takhtajan 1997), or their position has seemed to be completely uncertain (see above).