EMBRYOPSIDA Pirani & Prado (crown group)

Gametophyte dominant, independent, multicellular, thalloid, with single-celled apical meristem, showing gravitropism; flavonoids + [absorbtion of UV radiation]; protoplasm dessication tolerant [plant poikilohydric]; cuticle +; cell walls with (1->4)-ß-D-glucans [xyloglucans], lignin +; rhizoids unicellular; 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; diploid 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, sporangium +, single, with polar transport of auxin, 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]; spores trilete; close association between the trnLUAA and trnFGAA genes on the chloroplast genome.

Note that many of the bolded characters in the characterization above are apomorphies in the streptophyte clade along the lineage leading to the embryophytes rather than being apomorphies of the crown embryophytes.

STOMATOPHYTES

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; 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.

[Hornworts + Polysporangiophyta]: archegonia embedded/sunken in the gametophyte; sporophyte long-lived, chlorophyllous, nutritionally largely independent of the gametophyte; sporophyte-gametophyte junction interdigitate, sporophyte cells showing rhizoid-like behaviour.

POLYSPORANGIOPHYTA

Sporophyte well developed, branched, free living, sporangia several; spore walls not multilamellate [?here]; apical meristem +.

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 +); 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 ± monopodial; 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].

LIGNOPHYTA

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 with xylem and phloem originating on alternate radii, vascular tissue not medullated, 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 +; stem cork cambium superficial; branches exogenous; 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.; leaves with petiole and lamina, development basipetal, blade simple; axillary buds +, (not associated with all leaves); prophylls two, lateral; plant heterosporous, sporangia borne on sporophylls; microsporophylls aggregated in indeterminate cones/strobili; true pollen +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, parietal tissue 2+ cells across, megaspore tetrad linear, functional megaspore single, chalazal, lacking sporopollenin, megasporangium indehiscent; pollen grains landing on ovule; male gametophyte development initially endosporic, lacking chlorophyll, 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 landing 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; embryogenesis cellular; 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.]; (vessels 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, the 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 [5], G [3] 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.

[SANTALALES [BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDS]]] / ASTERIDS ET AL. / SUPERASTERIDS : ?

[BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDS]]: ?

[CARYOPHYLLALES + ASTERIDS]: seed exotestal; embryo long.

ASTERIDS - Sympetalae redux? - ASTERANAE Takhtajan   Back to Main Tree

Nicotinic acid metabolised to its arabinosides; (iridoids +); tension wood decidedly uncommon; C enclosing A and G in bud, (connate [sometimes evident only early in development, petals then appearing to be free]); anthers dorsifixed?; (nectary gynoecial); G [2], style single, long; ovules unitegmic, integument thick, endothelium +, nucellar epidermis does not persist; exotestal [!: even when a single integument] cells lignified, esp. on anticlinal and/or inner periclinal walls; endosperm cellular.

Age. The age of crown-group asterids has been estimated at ca 128 m.y., mid Early Cretaceous (K. Bremer et al. 2004); Wikström et al. (2003: c.f. topology) suggest an age of (122-)117, 107(-102) m.y., Janssens et al. (2009) an age of ca 128 m.y., while Anderson et al. (2005: only Cornales and Ericales sampled) give an age of ca 109 m.y.. Soltis et al. (2008) suggest ages of 130-115(-86) m.y.a. and Magallón and Castillo (2009) ca 106.35 m.y.; other estimates range from around (122-)114, 106(-100) m.y. (Bell et al. 2010), 167-103 m.y. (Schneider et al. 2004), (103-)93(-81) m.y. (N. Zhang et al. 2012), or as recently as (89-)84(-80) m.y.a. (Moore et al. 2010: 95% HPD).

Martínez-Millán (2010) evaluated the asterid fossil record, which for the most part is not very rich, and provided a series of fossil-based ages for asterid clades, with asterids going back to the Late Cretaceous ca 89.3 m.y. (Turonian), with Cornales, Ericales, and asterids I and II all being found in the fossil record by ca 83.5 m.y. (Late Santonian-Early Campanian). There are reports of earlier fossils, including Eoëpigynium burmensis, from 110-97 m.y. (Poinar et al. 2007; Poinar 2011 - flowers 4-merous, perhaps Cornales, but also perhaps Saxifragales, Myrtales, Asterales..., K quite well developed) and fossils of some 124 m.y. age that are perhaps Sarraceniaceae (Ericales) (Li 2005). Finally the Late Cretaceous Scandianthus (Friis & Skarby 1982) shows phenetic similarity with Vahliaceae, Hydrangeaceae, Phyllonomaceae, Escalloniaceae, and even some Saxifragaceae s. str. These earlier fossils are difficult to integrate into the phylogeny.

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. Cornales and Ericales may have diverged soon after the origin of the stem group asterids ca 128 m.y.a., mid Early Cretaceous, and the other asterid orders all diverged over 100 m.y.a. (K. Bremer et al. 2004)

Ericales and Cornales in particular show much variation in the degree of sympetaly, stamen number and development, adnation of stamens to corolla, and in ovule morphology and anatomy; some of this variation is like that found in rosids, Dilleniales, etc., and is unlike that in the asterids I + II. They may also have ellagic acid, which has a rather similar distribution; interestingly, Ericales and Cornales contain the only families in which both iridoids and ellagic acid occur (Cornaceae, Symplocaceae, Ericaceae and Fouqueriaceae - Bate-Smith 1984). For further discussion of this variation, see the euasterids.

Ecology & Physiology. Leaf size increases and plant height shows a notable decrease at this node (Cornwell et al. 2014), although the former character subsequently decreases both in Ericaceae and in the euasterids.

See Batashev et al. (2013 and literature) for the anatomy of minor-vein phloem (the typology is complex) and its physiological implications.

Plant-Animal Interactions. Iridoids, common in asterids, have been implicated in herbivore preferences, deterring some and attracting others (e.g. see discussion under Plantaginaceae, Scrophulariaceae, etc.: Bowers 1980, 1988; Dobler et al. 2011); iridoids have a bitter taste and are emetics for vertebrates, at least. However, they are sometimes sequestered by the insect eating the plant and used in its defence against predators (Dyer & Bowers 1996; Nishida 2002 for a summary) - confusing the issue, iridoids may also be synthesized de novo by the insect (Burse et al. 2009 - Chrysomelina). Preferences can be striking: Uraniidae (moths) are found on Dipsacales, Lamiales, Gentianales - and also Daphniphyllaceae (an iridoid-containing member of Saxifragales - see Lees & Smith 1991), while larvae of Nymphalidae-Melitaeini butterflies are also almost restricted to asterids, although they also quite common on Asteraceae and Acanthaceae, which, although asterids, lack iridoids; Melitaeini distinguish between plants with route I secoiridoids, which they eat, and route II decarboxylated iridoids, which they rarely eat (Wahlberg 2001). Pentzold et al. (2014) discuss way in which the insect can get around iridoid defences. Iridoids may also be involved in plant-plant relationships. Parasite Orobanchaceae may produce toxic iridoid aglucones in their hosts and so increase their effect on the latter (Rank et al. 2004), while iridoids from roots of Verbascum (Scrophulariaceae) may depress germination of competitors (Pardo et al. 2004).

Chemistry, Morphology, etc. Albach et al. (2001a) discussed iridoid distribution, etc., in the asterids, as do Soltis et al. (2005b). Mølgaard and Ravn (1988) and Rønsted et al. (2002) outlined the systematic utility of caffeic acid derivatives; chlorogenic acid, an ester of caffeic and quinic acid, is especially common in asterids, but also occurs elsewhere (see also also Lamiales and Boraginaceae in particular for other derivatives).

Characteristic of the whole clade - although with numerous exceptions (derived), is the Baileyan wood anatomical syndrome of predominantly solitary vessels, scalariform perforation plates, mainly opposite vessel pitting, very long vessel elements and fibres at least 800 and 2190 µm long respectively, non-septate fibres with distinctly bordered pits, and diffuse to diffuse-in-aggregates and scanty paratracheal axial parenchyma (Lens et al. 2008). Compound leaves are relatively uncommon in asterids, and when they occur the leaflets are often not articulated and/or distinct (but c.f. Araliaceae!), however, elements of development are largely identical in very different-looking compound leaves (Bharathan et al. 2002; Blein et al. 2008). Taxa with stipules are also fairly uncommon.

Taxa with apetalous flowers are uncommon in asterids, as are taxa with a tube-forming hypanthium (c.f. in rosids). Monosymmetry may have arisen some fifteen times here, with several reversals in Lamiales and Dipsacales (Jabbour et al. 2008: see also Donoghue et al. 1998; Ree & Donoghue 1999); monosymmetric flowers may have one, or rarely two, spurs (Jabbour et al. 2008).

How the corolla develops is of considerable interest. Sympetalae of older studies were defined largely by their sympetalous corolla, but some families here included in the asterids seem to be polypetalous. However, developmental studies like those of Erbar (1991) suggest that at least some apparently polypetalous taxa have a ring primordium very early on (see, for example, Reidt & Leins 1994), i.e., they show early sympetaly. (It is somewhat paradoxical that early corolla tube formation should often be linked with a corolla that appears to have separate petals at maturity!) However, the position of early initiation of the corolla tube on the tree is quite uncertain. Apiales, Asterales, and Dipsacales have many members with such initiation, as do both Oleaceae and Rubiaceae, "basal" or almost so in their orders in the lamiids, and so do some Cornales (see Erbar & Leins 2011 for a recent survey). Although sampling leaves much to be desired, but the condition of early initiation could conceivably be a synapomorphy for the asterids (see Erbar & Leins 1996b; Leins & Erbar 2003b for more details), even if the basic condition could still be flowers in which the petals were functionally free, at least at anthesis. However, there may be an association between early corolla tube formation and flowers with an inferior ovary (Ronse Decraene and Smets 2000) and families like Oleaceae with superior ovaries and apparently early corolla tube formation need more study from this point of view, and the character needs re-evaluation. Only in many Ericales and other asterids does the mature flower have a decided corolla tube, hence the tentative assignment of posession of a corolla tube as an apomorphy for [Ericales + other asterids]; taxa with a pronounced corolla tube quite often have late corolla tube initiation, the petal primordia initially being free.

The direction of contortion in flowers with contorted petals tends to be consistent (again, c.f. rosids, where it may be labile even within an individual - see Endress 1999, 2001b, 2010c)), although exactly where the switch might occur on the tree is unclear. Lee et al. (2004) suggest that the CRABS CLAW gene is expressed in the rather different nectaries in the rosids (receptacular nectary) and asterids (gynoecial nectary) that they sampled; Bernadello (2007) surveyed nectary variation in asterids.

Endress (2010c) noted that ovules in this clade are fequently unvascularized, although the exact distribution of this feature is unclear; taxa with vascularized ovules are also quite common (e.g. Guignard 1893). The integument, when single, is often dermal in origin, as is the inner integument of other angiosperms, while the outer integument is largely subdermal (but c.f. monocots: see Bouman 1984; de Toni & Mariath 2009 - I have not looked at this character in detail). Although the suggestion might then be that the single integument of asterids corresponds to the inner integument of many bitegmic angiosperms, sampling need to be improved, and given that a number of Cornales and Ericales in particular have bitegmic ovules, the evolutionary story is unlikely to be simple. Indeed, the nature of the single integument so common here has occasioned much specularion, and it may well be a composite structure (Bouman & Calis 1977). Certainly, many asterids also have anatropous ovules, and curvature of the ovules in other angiosperms is commonly associated with the presence of a second integument (Endress 2011b). In the characterizations below, the asterid seed coat is described as being testal, despite this uncertainy; the term "testa" technically refers to that part of the seed coat that is derived from the outer integument. Commonly only the outer epidermal layer of cells is thickened and lignified, and this mostly on the anticlinal and the inner periclinal walls. This type of seed coat was called the Ericaceous-type seed by Huber (1991), and he emphasized its wide distribution; note that Caryophyllales also have an exotestal seed. Arillate seeds are decidedly uncommon in asterids, in part because the seeds are frequently very small.

K. Bremer et al. (2001) suggest some morphological synapomorphies for asterid groupings. In general, where many characters are to be placed on the tree depends on resolution of relationships within Ericales and Cornales, and even then the pattern of gain-loss of some of these features is liable to be complex. Some characters common in asterids, including those of wood anatomy - for a survey of wood anatomy of Sympetalae in the old sense, see Carlquist (1992b) - probably have functional and logical linkages that also must be taken into account. Thus the presence of a tenuinucellate nucellus is linked with that of unitegmic ovules (see also Erbar & Leins 2011), the development of an endothelium (Kapil & Tiwari 1978), and a simple exotestal (see above) seed type (Netolitzky 1926); that of sympetalous monosymmetric flowers with epipetalous stamens, etc.

Phylogeny. See the Dilleniales page for discussion on the relationships of the asterids; Caryophyllales or Santalales (or the two as a combined clade) may be their sister group.

The monophyly of the asterids is well established (e.g. Olmstead et al. 1992, 1993, 2000; P. Soltis 1999); Albach et al. (1998) suggest the four main groupings recognised here. Relationships in phylogenies proposed by K. Bremer et al. (2001: analysis of 2 genes + morphology) and Albach et al. (2001b: analysis of four genes) are largely congruent; differences were almost entirely in taxa not assigned to orders by A.P.G. (1998), although many of these have since been placed in orders, relationships in the provisional Bayesian analyses of Lundberg (2001b, d) pointing the way. B. Bremer et al. (2002) provide an early comprehensive phylogeny of the clade, although with minimal sampling within families, using three coding and three non-coding chloroplast markers. Both B. Bremer et al. (2003) and Olmstead (2000) suggest that there is strong support for Cornales being the sister to all other asterids; see also Albach et al. (2001), Soltis et al. (2003) and J. Li and Zhang (2010). Although Hilu et al. (2003) reverse the positions of Cornales and Ericales, they sequenced the matK gene alone; Caiophora (Loasaceae) appears in Asterales, far separate from the other members of the family - a case of mistaken identity? Morton (2011: nuclear Xdh gene) found some support for an {Ericales + Cornales] clade, but sampling in the latter was poor (see also N. Zhang et al. 2012: weak support, nuclear genes); Qiu et al. (2010: four mitochondrial genes, support for relationships mercifully poor) found Ericaceae to be sister to a clade [paraphyletic Cornales + rest of asterids] while Lee et al. (2011) even found Vaccinium to be sister to Caryophyllales in some analyses, with Cyclamen sister to Panax.... Tank and Donoghue (2010) provide a largely resolved tree of relationships between asterid orders, and the topology of the tree here is the same as theirs (see Fiz-Palacios et al. 2011 for additional suggestions). For trees produced by analyses of 18S/26S nuclear ribosomal data, see (Maia et al. 2014); very few deeper relationships have much support.

Previous Relationships. The distinction between all other angiosperms and the asterids partly corresponds to the distinction between the crassinucellate and tenuinucellate groups of Young and Watson (1970, based on phenetic analyses). However, there are also substantial differences, for example, Young and Watson included Apiaceae-Araliaceae in their crassinucellate group. Philipson (1974) further emphasized the distinction between the crassinucellate and tenuinucellate groups of Young and Watson, linking the two via Celastraceae, Grossulariaceae and Brexiaceae (here Celastrales, Saxifragales, and Crossosomatales, all rosids and not immediately related to asterids); Theales, Primulales and Ebenales together made up a separate lineage (here part of Ericales). Later Philipson (1977) resurrected van Tieghem's (1901) names Unitegminae and Bitegminae for these two groups; integument number and nucellus condition are correlated. General morphology indeed suggests such relationships, as Hufford (1992a) found even with phylogenetic analyses - Theaceae, Paracryphiaceae, Apiaceae and Araliaceae were members of Rosidae (but Pittosporaceae were sister to Polemoniaceae).

Synonymy: Aquifolianae Doweld, Aralianae Takhtajan, Asteranae Takhtajan, Balsaminanae Doweld, Boraginanae Doweld, Brunianae Doweld, Campanulanae Reveal, Cornanae Reveal, Diapensianae Doweld, Dipsacanae Takhtajan, Ericanae Takhtajan, Escallonianae Doweld, Eucommianae Reveal, Gentiananae Reveal, Lamianae Takhtajan, Lecythidanae Reveal, Loasanae Reveal, Oleanae Takhtajan, Phellinanae Doweld, Primulanae Reveal, Solananae Reveal Sarracenianae Reveal, Theanae Reveal, Vahlianae Doweld - Asteridae Takhtajan, Cornidae Reveal, Ericidae C. Y. Wu, Lamiidae Reveal, Theidae Doweld - Asclepiadopsida Brongniart, Asteropsida Brongniart, Bignoniopsida Nees, Campanulopsida Bartling, Caprifoliopsida Endlicher, Coffeopsida Brongniart, Convolvulopsida Brongniart, Diospyropsida Brongniart, Ericopsida Bartling, Ligustropsida Meisner, Loniceropsida Brongniart, Myrsinopsida Bartling, Plantaginopsida Meisner, Primulopsida Brongniart, Rubiopsida Bartling, Selaginopsida Brongniart, Solanopsida Brongniart, Styracopsida Bartling, Verbenopsida Brongniart

CORNALES Dumortier   Main Tree.

Iridoids diverse, ellagic acid +, flavones 0; vessel elements with scalariform perforation plates; nodes 3:3; inflorescence cymose; (flowers 4-merous), C valvate, apparently free, tube formation early; A basifixed; G inferior, crowned with disc-like nectary, ventral carpellary bundles in the carpel wall [transseptal bundles, i.e. vascular bundles to ovules go over the top of the septum and then down; there are no bundles running up the central axis of the gynoecium]; ovules 1-2/carpel, apical; fruit drupaceous, with apical germination valve(s) in the stone, K persistent. - 6 families, 51 genera, 590 species.

Age. Wikström et al. (2001) suggest figures of (106-)101, 94(-89) m.y. for the age of crown group Cornales and Anderson et al. (2005) similar ages of 101-97 m.y.; Janssens et al. (2009) date the group to (117.1-)104(-90.9) m.y. and Bremer et al. (2004) to some 112 m.y.a.. Magallón and Castillo (2009) estimate 101.55 m.y. as its age, Lemaire et al. (2011b) an age of (123-)106(-92) m.y..

Fruits can be assigned to Cornales because of their distinctive anatomy and they are well represented in the fossil record (Manchester et al. 2007), being datable to the Cretaceous-Maastrichtian, ca 70 m.y. before present (Nyssa) and Coniacian, ca 87 m.y. before present (Takahashi et al. 2002: Hironoia - see also Martinez-Millán 2010).

The Late Cretaceous Silvianthemum suecicum, from rocks in southern Sweden ca 83.5 m.y.o., has tricolp(or)ate pollen, eight stamens (but a 5-merous perianth), the anthers appear to be dorsifixed, and there are three short, adaxially grooved styles (Friis 1990; see also Martínez-Millán 2010; Friis et al. 2011, 2013b). Bertilanthus scanicus, from the same rocks, has glandular hairs and stamens opposite the petals (Friis & Pedersen 2012). Although initially thought to be close to Quintinia (Paracryphiales), a position within Cornales was suggested by Beaulieu et al. (2013), which is more in accord with the morphology (and geography) of these fossils; Friis et akl. (2013b) opt for a close linkage of Quintinia and the fossils, but they think that the position of Quintinia may be incorrect.

Evolution. Divergence & Distribution. Endress (2011a) thought that the inferior ovary of Cornales might be a "key innovation" - but whether for all or just a part of the clade would depend on its topology, and anyhow the clade is not very speciose.

Chemistry, Morphology, etc. The strands of apotracheal parenchyma are relatively long (at least 9 cells long) in Cornaceae s.l. (inc. Curtisiaceae) when compared with some of their putative relatives (Noshiro & Baas 1998). Spirally-thickened vessels holding the two halves of transversely-torn leaves together are quite common... Teeth of Nyssaceae and Hydrangeaceae have a clear apex with a foramen, higher order laterals are involved (Hickey & Wolfe 1975). The petals may be free, but corolla tube formation, when known, is early (e.g. Reidt & Leins 1994).

For more details, see Faure (1924), Ferguson (1977: pollen), Sato (1976: embryology), Jahnke (1986: inflorescence of Cornaceae s.l.), Grayer et al. (1999: saponins).

Phylogeny. Molecular studies (e.g. Xiang et al. 1993) suggest a break-up of the old, broadly circumscribed Cornaceae; the core is here. Relationships between genera in this core have been unclear for some time, but at least some aggregation of the families they represent was clearly in order (e.g. Albach et al. 2001b; Xiang et al. 2002), indeed, relationships in Cornales as a whole were unclear. Although Cornus is sister to Mastixiaceae in some morphological trees (Murrell 1993), it is not nearly so close in rbcL trees (Xiang et al. 1993, 1997). For the relationships of Grubbiaceae and Hydrostachyaceae (placement of the latter is particularly difficult, see below), see especially Hempel et al. (1995), Xiang (1999), Soltis et al. (1997, 2000, 2007a), Savolainen et al. (2000b), Fan and Xiang (2003) and Xiang et al. (2002). There has been support for a sister group relationship between Grubbiaceae and Curtisiaceae for quite some time (e.g. Fan & Xiang 2001).

The phylogenetic position of Hydrostachyaceae, a much-modified aquatic herb, has long presented problems. The embryology of the family shows certain similarities with that of Crassulaceae, but relationships neither there nor with Podostemaceae (see below) can be maintained given what we now know about relationships of these clades. Members of sympetalous groups, especially Lamiales, show similarities to Hydrostachyaceae in ovary structure (apical septae) and in ovule and endosperm development. However, although the coenocytic micropylar haustorium is well developed, the chalazal endosperm cell, which remains undivided, is barely haustorial, and the two carpels are collateral, rather than superposed as in most Lamiales (Jäger-Zürn 1965; see also Rauh & Jäger-Zürn 1966, 1967 [strongly supporting a relationship with Lamiales]; Leins & Erbar 1988, 1990). However, in some Orobanchaceae (e.g.) the chalazal haustorium is also very poorly developed (Tiagi 1963), as in Lamiales basal to Calceolariaceae. A position within Hydrangeaceae has also seemed to be quite likely (Xiang 1999; see also Hempel et al. 1995; Olmstead et al. 2000; Albach et al. 2001; Wikström et al. 2001; Fan & Xiang 2001; Xiang et al. 2002; Bell et al. 2010 - even in Xiang et al. 2011 this position cannot be excluded), but note that Hydrostachyaceae has a very long branch; what about the mitochondrial coxII.i3 intron (Joly et al. 2001)? As Albach et al. (2001) note, few morphological characters support this position, but one could argue that this is perhaps to be expected of any highly-derived aquatic...

In a five-gene analysis Burleigh et al. (2009) found that there was strong support (97% ML bootstrap) for a position of Hydrostachys within Lamiales, largely because of the matK sequence added. Where in the Lamiales Hydrostachys might be placed was unclear, although it would probably be in a clade that excluded Oleaceae, at least. More comprehensive analyses are needed; Calceolaria and other clades below it in Lamiales other than Oleaceae were not sampled. Indeed, although morphologically Hydrostachyaceae are more or less at home in Lamiales (and I initially thought that they might end up there), more comprehensive analyses (Schäferhoff et al. 2010) exclude them from that order; a sequence used by Burleigh et al. (2009) was similar to that of Avicennia (Acanthaceae)... However, the focus of the work by Schäferhoff et al. (2010) was on relationships within Lamiales, so they did not place Hydrostachyaceae with confidence.

Recently, Xiang et al. (2011) found a set of relationships [[Cornaceae [Curtisiaceae + Grubbiaceae]], Nyssaceae s.l., [Hydrostachyaceae [Hydrangeaceae + Loasaceae]]]]. Here taxon sampling is good and many of the relationships are well supported, however, nuclear 26S rDNA data alone suggested somewhat different relationships than did the six chloroplast genes, with Hydrostachys being embedded in Cornaceae s.l. Chloroplast genes alone placed Nyssaceae with good support as sister to [Hydrostachyaceae [Hydrangeaceae + Loasaceae]], and relationships suggested by this chloroplast phylogeny are followed here (BEWARE: the tree has not yet been changed!), although there is little in the way of morphology to pin to the basal nodes. As Xiang et al. (2011) note, this new topology makes character evolution interesting.

Previous Relationships. 11/15 of the genera of Cornaceae s.l. have been placed in monotypic families, or the family has been circumscribed very broadly, as by Mabberley (1997). Previous inhabitants of the old Cornaceae may be found in Garryaceae (Garryales), Montiniaceae (Solanales), Argophyllaceae (Asterales) and Griseliniaceae (Apiales).



Includes Cornaceae, Curtisiaceae, Grubbiaceae, Hydrangeaceae, Hydrostachyaceae, Loasaceae, Nyssaceae.

Synonymy: Alangiales Martius, Grubbiales Doweld, Hortensiales J. Presl, Hydrangeales Martius, Hydrostachyales Reveal, Loasales Berchtold & J. Presl, Nyssales Martius, Philadelphales Link - This is the asterid IV group of some early phylogenetic studies.

[Cornaceae [Grubbiaceae + Curtisiaceae]]: sieve tube plastids also with polygonal protein crystalloids; leaves opposite, bases joined by a line/ridge; flowers small.

CORNACEAE Berchtold & J. Presl, nom. cons.   Back to Cornales

Cornaceae

Trees and shrubs (stoloniferous subshrubs); (plants Al accumulators), route I secoiridoids, also route II decarboxylated iridoids, isoquinoline alkaloids, triterpenoid saponins, flavonols, +, tanniniferous; (mucilage +); (laticifers +); (vessel elements with simple perforation plates); sclereids +; petiole bundle(s) arcuate (with adaxial inverted plate [and with wing bundles]), or D-shaped or annular (with inverted medullary bundle); hairs T-shaped, unicellular, (stellate), walls often with crystals; (leaves spiral or two-ranked), lamina vernation conduplicate(-flat) or curved (both -plicate) or involute, margins entire (lobed), secondary veins pinnate or actinodromous; flowers 4(-10)-merous; K notably small, connate or not; stamens = and opposite sepals (-4x, anthers long - Alangium); pollen with complex endaperture [a pore joining two lateral thinnings parallel to the colpus], often starchy; G [1-4], (1 loculus), style short (long, with long arms), stigma truncate to capitate, dry; ovules apotropous, parietal tissue ca 3 cells across (0 - red-fruited Cornus), hypostase 0; (megaspore mother cells several), (embryo sac tetrasporic, 8-nucleate, antipodals polyploid [Fritillaria type]); drupe 1-2-seeded, walls with sclereidal cells; testa of elongated cells, much compressed, (ca 6 cells thick, vascularized - Alangium); endosperm (also nuclear), hemicellulosic, embryo green; n = 8-11.

2[list]/85: Cornus (65). Scattered, not S. South America (map: see van Steenis & van Balgooy 1966; Aubréville 1974; Fl. Austral. 8. 1984; Meusel et al. 1978; Hultén & Fries 1986; Xiang & Thomas 2008; Trop. Afr. Fl. Pl. Ecol. Distr. 6. 2011). [Photos - Habit, [Photo: Cornus Inflorescence, Flower, Fruit.]

Age. An age of (82-)67(-47) m.y. is suggested for crown-group Cornaceae (Bell et al. 2010); Wikström et al. (2001) suggest an age of (79-)73, 64(-58) m.y..

Divergence & Distribution. Xiang and Thomas (2008) thought that stem-group Cornus was Late Cretaceous in age, ca 80 m.y. old, substantial diversification having occurred by ca 66 m.y.a.. Fruits of Cornus subg. Cornus have distinctive alveolate endocarps and are known from the Palaeocene of North Dakota in rocks about 58 m.y. old; they have six locules (Manchester et al. 2010b).

Pollination Biology. The floral organ B (some, but not all, i.e. not PI, but AP3) and C genes are expressed in the large, white inflorescence bracts of Cornus, a heterotopic shift that has occurred at least twice (Maturen et al. 2005; Xiang et al. 2010; Zhang et al. 2008: extensive PI-like gene duplication; Feng et al. 2012).

Chemistry, Morphology, etc. Blue-fruited dogwoods have lost iridoids (Xiang et al. 1997). In nodes of Alangium the central vascular trace may immediately divide into three (nodes 3:5). Mabberley (1997) describes Alangiaceae as having spiral leaves; they are often two-ranked. In Alangium there is a very little vascular tissue in the center of the ovary, while there is considerable variation in embryo sac development in Cornus in particular (Johri et al. 1992 for references).

For further information, see Fagerlind (1939c: embryo sac), Adams (1949: anatomy), Mittal (1961: some petiole anatomy) and Eyde (e.g. 1968, 1988: flower and fruit in particular), Neubauer (1978: petiolar anatomy), Jensen et al. (1975a: iridoids), Kubitzki (2004b: general), and Feng et al. (2011: inflorescence morphology and evolution).

Phylogeny. For a careful study of reconstructing ancestral areas and characters in Cornus, see Xiang and Thomas (2008); the results depended much on the methods used, etc. For relationships within Cornus, c.f. Murrell (1993) and Xiang et al. (1993, 2006), and for relationships within Alangium, see Feng et al. (2009).

Botanical Trivia. The anthers of Cornus canadensis have explove dehiscence; the maximum acceleration rate of the pollen grains has been estimated at 24,000 m/s2 (Edwards et al. 2011).

Synonymy: Alangiaceae Candolle, nom. cons.

[Grubbiaceae + Curtisiaceae]: style short, lobed; ovule one/carpel, epitropous, parietal tissue 0; walls of stone made up of sclereids; endosperm copious.

Age. The age of this clade is ca 90 m.y., suggesting that it is very much a relict in the Cape flora (Warren & Hawkins 2006). Since fossil fruits of Curtisia have been identified in the Eocene of southern England (Manchester et al. 2007), its history is likely to be quite complex.

Chemistry, Morphology, etc. For characters holding these two families together, see in part Xiang et al. (2002).

Classification. Xiang et al. (2002) suggested that Grubbiaceae and Curtisiaceae might be combined, but they are kept separate here because they are rather different in appearance (see also A.P.G. III 2009).

GRUBBIACEAE Meisner, nom. cons.   Back to Cornales

Grubbiaceae

Evergreen ericoid shrubs; iridoids 0?; sieve tube plastids?; subepidermal collenchyma +; hairs unicellular; cuticle waxes as long narrow platelets; lamina margins revolute; inflorescences axillary, capitate or cone-like; flowers also 6-merous; K valvate, C 0; A 8, 12, anthers inverted, bisporangiate, monothecal; G [2], transverse, placentation axile at base, becoming free-central; nectary hairy; ovule integument "thick", micropyle "long"; fruit a syncarp, seed [per fruit proper] 1, coat thin; endosperm ?type, micropylar and chalazal endosperm haustoria +, embryo long; n = ?

1[list]/3. Cape Province, South Africa (map: from Vester 1940).

Chemistry, Morphology, etc. The family is poorly known. The inversion of the anther is very comprehensive in Grubbiaceae, and for some (e.g. Fagerlind 1947b) this has suggested relationships with Ericaceae. Carlquist (1978a) found Grubbiaceae to be anatomically identical to Bruniaceae (Bruniales, a campanulid), c.f. also Geissolomataceae (rosid-Crossosomatales).

Some information is taken from Dahlgren and van Wyk (1988) and Kubitzki (2004b), both general, Schnizlein (1843-1870: fam. 18 - carpel orientation), and Fagerlind (1948b: embryology).

Synonymy: Ophiraceae Arnott

CURTISIACEAE Takhtajan   Back to Cornales

Curtisiaceae

Evergreen trees; route I secoiridoids +, ?ellagic acid; ?nodes; petiole bundle annular, with medullary strands; single crystals +; lamina vernation ± flat, margins serrate; inflorescence terminal; K small, open; stamens = and opposite sepals; pollen with H-shaped endapertures; G [2-4], with axial/central vascular bundles; fruit 4-seeded; endotesta tanniniferous, rest ± collapsed; ?endosperm haustoria, embryo minute; n = 13.

1/1: Curtisia dentata. Southern Africa (map: from Palgrave 2002; Yembaturova et al. 2009; fossil [blue] from Manchester et al. 2007a]). [Photo - Fruit]

Evolution. Divergence & Distribution. Manchester et al. (2007a) recognised the distinctive fruits of Curtisia from the Eocene of southern England; the fossils were originally described under Epacridaceae (= Ericaceae - Styphelioideae).

Chemistry, Morphology, etc. Takhtajan (1997) described the hairs of the branchlets, petioles and inflorescences of Curtisia as being stellate; they are simple and curled. The "plications" (Cullen 1978) in the young leaves are in fact only prominent veins. Curtisia is embryologically unknown, but it lacks transseptal bundles, having the "normal" central bundles.

For general information, see Kubitzki (2004b).

Classification. See Yembaturova et al. (2009).

[Nyssaceae [Hydrostachyaceae [Hydrangeaceae + Loasaceae]]]: ?

NYSSACEAE Dumortier, nom. cons.  Back to Cornales

Nyssaceae

Trees and shrubs;(Al accumulators); route I secoiridoids, triterpenoid saponins, (resin), +, tanniniferous, (mucilage +); (laticifers +); (leaf traces running along the stem - Mastixia), (sclereids +), pith septate or not; petiole bundles arcuate or with adaxial plate; (stomata paracytic); hairs T-shaped, unicellular; leaves spiral (opposite), lamina vernation conduplicate [Nyssa], margins serrate or entire; plants andromonoecious, dioecious, etc., or flowers perfect; inflorescences various, racemose (capitate); flowers 4-5-merous, small; K notably small, C ± imbricate, or valvate and inflexed at apex and with a median ridge, or P 0; A 4-26 [often diplostemonous]; pollen with complex endaperture [a pore joining two lateral thinnings parallel to the colpus]; G [5-10], (1 locular, ovule 1 - Nyssa), style short, (long - Nyssa; styles +); ovules epitropous, micropyle long, integument ca 8-10(-15+) cells across, parietal tissue 1-3 cells across, (nucellar cap ca 2 cells across), suprachalazal zone much elongated, hypostase +, supraraphal chalaza massive, (pachychalazal), (endothelium +); (megaspore mother cells several); fruits 1-5-seeded, drupe walls of fibrous cells [?an apomorphy]; (seed U-shaped - Mastixia), testa multiplicative, exotesta lignified, cells polygonal; (endosperm also nuclear), embryo long or short; n = 11, 13 [both Nyssa], 21, 22.

5/22. Mainly East Asia, also Indo-Malesia and E. North America (map: see van Steenis & van Balgooy 1966; Matthew 1977). [Photo - Nyssa Flower, Fruit © H. Wilson.]

Evolution. Divergence & Distribution. For the early Tertiary fossil history of what are now East Asian endemic genera of Nyssaceae, see Manchester et al. (2009 and references). Fossils of mastixioid fruits in particular are widespread in the northern hemisphere in the Late Cretaceous and early Tertiary, some being 3- or 4-carpellate; they are placed in 8 genera and 33 species (Eyde & Guinn 199; Eyde 1997, for details), Mastixia being especially abundant in Europe and Siberia 65-70 m.y.a. (Manchester 2002).

Pollination Biology. Davidia has perianth-less flowers in capitula that are subtended by 2 large white bracts; expression of B-class floral genes in these bracts is implicated (Vekemans et al. 2011).

Plant-Animal Interactions. For the indole alkaloid camptothecin, see Lorence and Nessler (2004). The enzyme that camptothecin targets is in the plant, but the plant is probably protected by changes in its amino acid sequence, one of which (serine in position 722) is the same as is found in camptothecin-resistant tumours in humans (Sirikantaramas et al. 2009). Camptothecin is sequestered in glandular hairs although not in the laticifers (Hagel et al. 2008).

Chemistry, Morphology, etc. Diplopanax contains petroselenic acid (Zhu et al. 1998). Although Zhu et al. did not find petroselenic acid in Fatsia (Araliaceae) or Aucuba (Garryaceae), it is found in a number of Apiales, and relationships between Cornaceae and some Apiales have been suggested in the past...

Mohana Rao (1973a) described the integument of Nyssa as being ca 5 cells across and the ovules as being tenuinucellate. However, the integument is much thicker when the embryo sac is mature (Fig. 5G), and a single subepidermal layer of cells is shown between the embryo sac and epidermis (Fig 3D, E); epidermal cells on occasion divide periclinally, but such divisions seem not to account for this subepidermal layer.

Davidia lacks a perianth and may have bitegmic ovules (but c.f. Horne 1914). Diplopanax has recently been placed in Mastixiaceae s. str. (Eyde & Quiyun 1990; c.f. Xiang et al. 1997). It has five lobes on the disc opposite the corolla and a single-seeded fruit the embryo of which is C-shaped in transverse section (Ying et al. 1993); see above for chemistry.

For some embryology, see also Horne (1909, 1914), Tandon and Herr (1971), for cytology, see He et al. (2004), for general information, see Kubitzki (2004). For Mastixia, see Matthew (1976); embryological details are unknown for it, Diplopanax, etc.

Synonymy: Davidiaceae H.-L. Li, Mastixiaceae Calestani

[Hydrostachyaceae [Hydrangeaceae + Loasaceae]]: ovules many/carpel, parietal tissue 0; ovary with intrusive parietal placentation; micropylar endosperm haustorium +.

HYDROSTACHYACEAE Engler, nom. cons.   Back to Cornales

Hydrostachyaceae

Annual to perennial herbs; submerged aquatics; primary root 0, adventitous roots +; kaempferol +, iridoids 0; vessels present, ?type; nodes ?; stomata 0; leaves spiral, deeply and complexly divided, surface with small enations, stipule single, intrapetiolar (two, lateral); inflorescence spicate, plants di(mon)oecious; P 0; nectary 0; staminate flowers: A 2, extrose, monothecal; pollen in tetrads, inaperturate; carpellate flowers: G superior, [2], transverse, style branches separate, filiform, impressed in the apex of the ovary; ovules with integument ca 5 cells across, ?endothelium; fruit a septicidal capsule; seeds minute, exotestal, outer cell walls much thickened, mucilaginous; endosperm scanty or 0; n = 10-12.

1[list]/20. C. and S. Africa, Madagascar (map: from Rauh & Jäger-Zürn 1966b; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010).

Chemistry, Morphology, etc. The caffeoyl ester chlorogenic acid is found here and in the Loasaceae-Hydrangeaceae clade (Rønsted et al. 2002). Another interpretation of the androecium is that is consists of one tetrasporangiate stamen. Vessels are reported (Jäger-Zürn 1998), but are not described. There seems not to be an endothelium. The styles are more or less impressed into the apex of the ovary, a feature that Leins and Erbar (1988) noted was common in Lamiales, although I do not know the general distribution of this feature.

For floral development, see Leins and Erbar (1988), for general information, see Erbar and Leins (2004a), and for chemistry, Rønsted et al. (2002).

Previous Relationships. Hydrostachyaceae have variously been suggested as being sister to Decumaria (Hydrangeaceae) (Albach et al. 2001), or close to Crassulaceae (Saxifragales), or - perhaps - close to Podostemaceae (now near Hypericaceae, in Malpighiales). However, Takhtajan (1997) included Hydrostachyales in his Lamiidae, Cronquist (1981) also put Hydrostachyaceae in that general area, and Burleigh et al. (2009) also suggested they might be in Lamiales.

[Hydrangeaceae + Loasaceae]: similar route I secoiridoids and route II decarboxylated iridoids [C-8 iridoid glucosides +; C-9 iridoids, keeping the C-11, e.g. deutzioside, +], flavonols +, ellagic acid 0; cork cambium deep-seated; hairs tuberculate, walls calcified, with basal cell pedestals; leaves opposite, lamina (lobed), margins with glandular teeth; A (initiated as antesepalous triplets), (2x C-)many; ovary with axial/central vascular bundles, stigma dry; ovules with endothelium; fruit septicidal, (persistent placental strands +); exotestal cells variously elongated, inner walls thickened; chalazal endosperm haustorium +; mitochondrial coxII.i3 intron 0.

Age. A possible age for this node is (64-)50, 49(-36) m.y. (Bell et al. 2010), while Wikström et al. (2001) suggest an age of (96-)91, 82(-77) m.y..

Chemistry, Morphology, etc. For the distinctive iridoids of this family pair, see Frederiksen et al. (1999).

The androecium of both families is very variable in development (Hufford 1990, 1998). It is possible that diplostemony is plesiomorphic, with polystemony derived. The antisepalous androecial triplets sometimes found here are also found in Rosaceae and Zygophyllaceae (Hufford 2001b, see also Ronse Decraene & Smets 1996a). The embryology of the group is poorly studied. Fruits are sometimes septicidal and sometimes loculicidal; this variation has not been integrated with the phylogeny.

Classification. Takhtajan (1997) included Hydrangeales in Cornidae-Cornanae, but Loasales-Loasanae were part of his Lamiidae.

HYDRANGEACEAE Dumortier, nom. cons.   Back to Cornales

Shrubs, vines, or herbs; (plants Al accumulators); kaempferol, flavonols +, tanniniferous; (hairs stellate or branched); cork inner cortical or outer pericyclic; (vessel elements with simple perforation plates); true tracheids +; (stomata paracytic); leaves opposite, bases joined by lines across the stem, lamina vernation conduplicate or supervolute, (secondary veins palmate); inflorescence cymose; flowers 4-5(-10)-merous; (stamens with flattened filaments, forming a tube), anthers with basal pit; tapetal cells 1-4-nucleate; nectary vascularized; G [(2-)3-5(-12)] to inferior, ovary ribbed, arrangement variable, (style branched, adaxially channeled), stigma linear to capitate; ovules apotropous, integument (3-)5-7(-10 - Hydrangea) cells across; embryo sac protruding into micropyle, antipodal cells persist; seed winged or not; endosperm moderate, micropylar endospermal cell elongated; n = 13-18.

17[list]/190 - divided into two subfamilies, and one subfamily into two tribes. Warm temperate, some species in tropics. [Photo - Flower] [Photos - Collection]

Age. The age for crown Hydrangeaceae may be (87-)83, 69(-65) m.y.a. (Wikström et al. 2001) or (58-)44, 43(-30) m.y. (Bell et al. 2010); both include Hydrostachyaceae.

Some of the Late Cretaceous fossils assigned to Esgueiria and placed in Combretaceae may end up here - c.f. style, hair surface, etc. (see Takahashi et al. 1999). The Late Cretaceous Scandianthus from Sweden, has also been linked with Hydrangeaceae (see Friis & Pedersen 2012 for references), as has Tylerianthus, also Late Cretaceous but from North America (Gandolfo et al. 1998b: mostly compared with Saxifragaceae s. str.).

Jamesioideae

1. Jamesioideae Hufford

Nothing obvious! (Myricetin +); leaf buttresses prominent after leaves fall; K valvate, C free; A 10; G (3-)4-5, style branches separate or almost so; endothelium 0, basal part of nucellus persists [Fendlera]; endosperm nuclear [Fendlera]; n = 16.

2 (Jamesia, Fendlera)/ca 5. W. North America (map: from Holmgren & Holmgren 1989).

2. Hydrangeoideae Burnett

Nodes also 5:5, 7(+):7(+); petiole bundles (arcuate [+ inverted bundles]) annular, often with medullary bundles; raphide sacs + (0); stomata variable; (hairs stellate); K valvate, (C contorted); microsporogenesis simultaneous [Platycrater]; (archesporial cells several), embryo sac long [inc. long chalazal half], grows out of micropyle; (placentation axile).

Hydrangeoideae

15/185. Warm temperate, esp. South East Asia and North America, S. to Chile and Malesia (map: from Hu 1955; Zaikonnikova 1966; McClintock 1957; van Balgooy 1984; Mai 1985; Hong 1993).

Age. The age of crown Hydrangeoideae is estimated at (82-)78, 67(-63) m.y.a. (Wikström et al. 2001: note position of Hydrostachys!).

2a. Philadelpheae

(Stomata laterocytic); (K connate), C imbricate; A 10, or many and initiation as five common primordia; style ± branched or not; ovule with 1 lateral layer of nucellar tissue; embryo sac ± protruding from the nucellus.

6/130: Philadelphus (65), Deutzia (60). Warm temperate, esp. South East Asia to the Philippines, SW North America, also Central America, Philadelphus coronarius in Europe.

Synonymy: Philadelphaceae Martynov

2b. Hydrangeeae

Myricetin + [Decumaria]; raphides +; inflorescence often with conspicuous marginal flowers; C valvate; style branches separate; fruits loculicidal, (baccate).

9/65. Warm N. temperate, S. to Chile and Malesia.

Chemistry, Morphology, etc. Species of Deutzia have stamens in a single whorl with strongly flattened filaments that may form a tube around the ovary and style, and a similar arrangement seems to be sporadic in the family (e.g. see also Jamesia). Philadelphus shows centrifugal androecial development. In Philadelphus, Dichroa and Deutzia the four carpels alternate with the sepals, or there are three carpels with the odd member adaxial; in Hydrangea the odd carpel is abaxial, while in Broussaisia the five carpels are opposite the sepals. There is considerable variation in the degree of fusion of the styles, but transitions between the extremes are easy to envisage (Roels et al. 1997). In a number of taxa the embryo sac more or less protrudes into the micropyle or beyond (Maheshwari 1950; Hufford 2004). The presence of chalazal haustoria needs confirmation; Mauritzon (1933) noted that the antipodal cells might persist, as in Kirengeshoma, and talks of an "Antipodenhaustorium". The base of the endosperm is lignified; Fendlera has nuclear endosperm (Mauritzon 1939a). The endocarp of Hydrangea consists of large cells with digitate-interlocking anticlinal walls, as in Curtisia, but not in Cornus (Manchester et al. 2007).

For iridoids, see Frederiksen et al. (1999) and for flavonoids, see Bohm et al. (1985), for vegetative anatomy, see Watari (1939), Styer and Stern (1979 and references) and Gornall et al. (1998), for variation in the position of the carpels when the gynoecium is bicarpellate, see Eichler (1878; also Eckert 1966), for floral anatomy and morphology, see Klopfer (1971, 1973) and Bensel and Palser (1975c), for androecial development, Gelius (1967) and Hufford (1998, 2001a), for floral morphology of Hydrangeae, see Hufford (2001), for some embryology, etc., see Gaümann (1919: Philadelphus), Mauritzon (1933, 1939a) and Ao (2008), for seeds, see Hufford (1995, 1997) and Nemirovich-Danchenko and Lobova (1998), and for general information, see Hufford (2004).

Phylogeny. For relationships within the family, see Hufford (1997b), Hufford et al. (2001: support for its monophyly is not overwhelming), and Soltis et al. (1995a). Samain et al. (2010b) and Mendoza et al. (2012) discuss relationships in Hydrangeeae, where Hydrangea is polyphyletic.

Classification. For a classification of Hydrangeaceae, see Hufford et al. (2001); generic limits around Hydrangea are a mess - Platycrater is embedded in Hydrangea s. str. and the latter will probably have to be divided (Samain et al. 2010b; Mendoza et al. 2012).

Previous Relationships. Hydrangeaceae were part of the old woody Saxifragaceae/Saxifragales, or included with members of this group in Rosales (e.g. Cronquist 1981).

Synonymy: Hortensiaceae Martinov, Kirengeshomaceae Nakai

LOASACEAE Jussieu, nom. cons.   Back to Cornales

Loasaceae

Often coarse herbs (shrubs); myricetin, tannins 0; cork inside pericycle; vessel elements with simple perforation plates; petiole bundles arcuate or annular, with wing bundles; trichomes glochidiate (stinging), often silicified; leaves spiral (opposite), (compound), lamina (margins lobed), secondary veins pinnate-palmate; flowers (4-)5(-7)-merous; K connate, C with three traces, ?valvate; C-A synorganisation, C-A plate formed, filaments terete; pollen tectum striate; G [5], (± superior), opposite sepals, (3, odd member adaxial), style hollow, lobed, stigma narrow or clavate; ovules epitropous, integument 12-17 cells across; (fruit spirally twisted); (testa with hypodermal layer thickened); endosperm copious to none.

14[list]/265 - five clades below. Mostly American, but also Africa and the Marquesas Islands (map: from Heywood 1978).

Age. A possible age for Loasaceae is (44-)33, 31(-21) m.y. (Bell et al. 2010) or (73-)67, 63(-57) (Wikström et al. 2001).

1. Eucnide

(C connate), A (adnate to C), centripetal, connate basally; fruit a septicidal capsule; n = (?19-)21.

1/15. S.W. North America. [Photo - Eucnide Flower © J. Reveal]

2. Schismocarpus

A 10, filaments shorter than the anthers; G opposite petals, stigma capitate.

1/1: Schismocarpus pachypus. Mexico.

[Loasoideae [Mentzelioideae + Gronovioideae]]: G [3-5], when [3], odd member adaxial.

3. Loasoideae Gilg

K and C shed separately, petals cymbiform, clawed; A centripetal and centrifugal, stamens in 5 groups opposite petals, antesepalous staminodes + [outer whorl connate, as scales, inner whorl separate, more elaborated]; pollen ?not striate; n = 6.

Nasa (105). America, but also Africa (Kissenia) and the Marquesas Islands (Plakothira). [Photo - Flower, Flower, Flower, Fruit, Flower.]

[Mentzelioideae + Gronovioideae]: loss of C-A synorganisation.

4. Mentzelioideae Gilg

K and C quincuncial, shed as a unit; A centripetal, connate basally, (forked staminodes +); n = 7.

Mentzelia (60). [Photo - Flower © S. Wolf.]. America.

5. Gronovoioideae M. Roemer

(Hypanthium +), C valvate, petals with a single vascular trace; A 5, opposite sepals (2, three staminodes), anthers bifacial; G [3]; ovule 1/carpel, apical, crassinucellate [Petalonyx, Gronovia], funicular obturator +; fruit a cypsela; testa none; endosperm haustoria 0.

[Photo - Gronovia Flower.] America.

Synonymy: Cevalliaceae Grisebach, Gronoviaceae Endlicher

Evolution. Divergence & Distribution. Schenk and Hufford (2008) suggest dates for some of the main clades in the family.

Pollination Biology. There are some remarkable floral morphologies in the family. Weigend and Gottschling (2006) discuss pollination in Nasa; there are revolver flowers in the genus. Polination of some South American taxa by small mammals is likely, and in general nectar amount and sugar concentration increase with altitude (Ackermann & Weigend 2006).

Plant-Animal Interactions. In general Loasaceae from drier environments and in danger of being eaten by mammals contain a diversity of iridoids; interestingly, genera like Nasa that can be defoliated by pyralid caterpillars have little in the way of iridoids, but Nasa in particular has a great diversity of leaf shape (Weigend et al. 2000).

Chemistry, Morphology, etc. There is variation in the composition of fatty acids in the seeds, but its systematic significance is unclear. Of the taxa studied by Weigend et al. (2004b), Nasa (Loasoideae) was most distinct; it is well embedded in the family. In some species of Petalonyx (Gronovoideae) there is postgenital fusion of the corolla, this forces the stamens outside the corolla. For the complexities of androecial initiation, see Hufford (1990); antepetalous stamens arise from the flanks of primordia of antisepalous stamens. Hufford (2003) described staminode evolution in detail. The stigma is at least sometimes very long (Loasa triphylla - see Hanf 1935).

Additional information is taken from Thompson and Ernst (1967: Eucnide), Rodriguez et al. (1997) and Weigend et al. (2000: both iridoids), Leins and Winhard (1973), Brown and Kaul (1981), Weigend (1996), Hufford (1988, 1989, 1990), all floral morphology/development, and especially Moody and Hufford (2000a) and Weigend (2004: general).

Phylogeny. Strongly supported relationships suggested by Moody and Hufford (2000a), Moody et al. (2001), Hufford et al. (2003) and Hufford (2003) are Eucnide [Schismocarpus [Loasoideae [Mentzelioideae + Gronovioideae]]]. Within Loasoideae, the clade [Plakothira + Klaprothia + Kissenia] may be sister to the rest, but that relationship has little support (Hufford et al. 2005), or the clade may be part of a major polytomy (see also Weigend et al. 2004a). The distribution of the [Plakothira + Klaprothia + Kissenia] clade is remarkable - the Marquesas, South America, Africa...

Previous Relationships. In older classification Loasaceae were often grouped with other families that had parietal placentation (Cronquist 1981).