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.
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.
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, sporangia derived from periclinal divisions of several epidermal cells, wall multilayered [eusporangium]; columella 0; tapetum glandular; stellate pattern split between doublet and triplet regions of transition zone; placenta with single layer of transfer cells in both sporophytic and gametophytic generations, embryo with roots arising lateral to the main 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].
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 first endo- then exosporic, 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, embryo axis straight, so 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.
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; tapetal 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 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 20-20,000 µm/hour, outer wall pectic, inner wall callose, 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, becoming much larger than ovule at time of fertilization; endosperm diploid, cellular [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 , 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.
[DILLENIALES [SAXIFRAGALES [VITALES + ROSIDS s. str.]]]: stipules + [usually apparently inserted on the stem].
[SAXIFRAGALES [VITALES + ROSIDS]] / ROSANAE Takhtajan / SUPERROSIDAE: ??
[VITALES + ROSIDS] / ROSIDAE: anthers articulated [± dorsifixed, transition to filament narrow, connective thin].
ROSIDS: (mucilage cells with thickened inner periclinal walls and distinct cytoplasm); embryo long; genome duplication; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.
ROSID I / FABIDAE / [ZYGOPHYLLALES [the COM clade + the nitrogen-fixing clade]]: endosperm scanty.
[the COM clade + the nitrogen-fixing clade]: ?
Age. The age for this node is estimated to be about 78.1 m.y. by Xue et al. (2012).
[CELASTRALES [OXALIDALES + MALPIGHIALES]] / the COM clade: seed exotegmic, cells fibrous. Back to Main Tree
Age. The crown age of this group was estimated as (108-)104(-100) or (95-)91(-87) m.y. (two penalized likelihood dates); Bayesian relaxed clock estimates were slightly older, to 108 m.y. (Hengcheng Wang et al. 2009). Wikström et al. (2001) suggested an age of some (97-)94, 89(-86) m.y., rather like the ca 88.3 m.y. in Naumann et al. (2013), N. Zhang et al. (2012: Oxalidales not included) an age of (90-)81(-70) m.y., Magallón and Castillo (2009) an age of around 102 m.y., and Bell et al. (2010: note topology) ages of (111-)104, 101(-97) m.y..
Endress (2011a) suggested that a key innovation around here might be incompletely tenuinucellate ovules.
Chemistry, Morphology, etc. Endress and Matthews (2006a) suggest that an inner integument that is thicker than the outer is common in the COM clade, although this appears not to be the case for Celastrales; this character is not optimised to this part of the tree here, but see within each order. Endress and Matthews (2006a) also note that members of the COM clade commonly have a relatively thin nucellus and arillate seeds. A number of Malpighiales, including Linaceae, have a fibrous exotegmen similar to that of Oxalidales. In Celastrales, a similar exotegmen is found in Lepidobotryaceae, but not Celastraceae, given the departure of Perrottetia to Huerteales and Bhesa to Malpighiales (Zhang & Simmons 2006).
Phylogeny. This clade of three orders is often retrieved (e.g. P. Soltis et al. 1999: weak support), Zhang and Simmons (2006), Zhu et al. (2007: mitochondrial matR gene, but appreciable support only when chloroplast genes added), Hengcheng Wang et al. (2009), Qiu et al. (2010), etc. However, Oxalidales (it is probably best to include Huaceae there) have been found to be sister to the other two orders in some analyses (e.g. Zhu et al. 2007, but support very weak); support weakened when chloroplast genes were added (see also Soltis et al. 2007a; Bell et al. 2010). Relationships are unclear in Moore et al. (2011).
Similarity in seed coat anatomy had suggested relationships between families now placed in Malpighiales and Oxalidales (and also Zygophyllales) to authors like Corner (1976), Dahlgren (1991) and Boesewinkel (1994).
CELASTRALES Link Main Tree.
Vessel elements with simple perforation plates; tension wood ?; mucilage cells; stomata ?; lamina teeth?, stipules +; inflorescence cymose; flowers small; K quincuncial; micropyle bistomal; chloroplast infA gene present. - 2 families, 94 genera, 1355 species.
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...
Age. The age of crown-group Celastrales was estimated as (87-)81(-75) or (62-)56(-50) m.y. (two penalized likelihood dates); Bayesian relaxed clock estimates were up to 100 m.y. (Hengcheng Wang et al. 2009) [Check].
Chemistry, Morphology, etc. For possible additional synapomorphies of this clade, see Matthews and Endress (2005b, 2006). For instance, there is distinctive postgenital carpel closure by conspicuously elongated cells, and functionally imperfect flowers are common. All Celastrales are basically synascidiate.
Phylogeny. Huaceae were placed in this area by Nandi et al. (1998), and as sister to rest of Celastrales (inc. Lepidobotryaceae, when in the analysis), but with only moderate support, by Savolainen et al. (2000a, b); they were, however, not obviously close at all in Simmons et al. (2001 - Lepidobotryaceae not included) and were placed sister to Oxalidales with moderate support in Zhang and Simmons (2006; see also Soltis et al. 2011, etc.).
Includes Celastraceae, Lepidobotryaceae.
Synonymy: Brexiales Lindley, Hippocrateales Berchtold & J. Presl, Parnassiales J. Presl, Stackhousiales Martius
LEPIDOBOTRYACEAE J. Léonard, nom. cons. Back to Celastrales
Tree; cork?; wood fluoresces; nodes also 2:2 [Lepidobotrys]; cristarque cells in bundle sheath; stomata paracytic; leaves two-ranked, lamina articulated with petiole, margins entire, stipel +, single, long, (stipules adnate to petiole); plant dioecious; inflorescences terminal, congested; K and C similar in size; A 10, of two lengths, ± connate basally, anthers basifixed; nectary on inside of staminal tube; G [2-3], styles ± separate, stigmas capitate or style short, stigma lobed; ovules 2/carpel, collateral, apical, pachychalazal, epitropous, outer integument 7-10 cells across, inner integument ca 4 cells across [Ruptiliocarpon], parietal tissue ca 10 cells across, funicular obturator +; fruit a septicidal capsule, endocarp distinct, columella persisting; seed arillate, integuments multiplicative, (exotegmen not fibrous - Lepidobotrys); endosperm 0; n = ?
2[list]/2-3. West Africa (Lepidobotrys staudtii), Central and South America, scattered, to Peru (Ruptiliocarpon caracolito) (map: from Hammel & Zamora 1993; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003; Heywood 2007; Tropicos iii.2014). [Photo - Fruit]
Chemistry, Morphology, etc. Ruptiliocarpon, at least, has distinctive spirotriterpenoids unique to flowering plants (Asim et al. 2010). There is no evidence other than morphology (articulation, stipels) that the apparently simply leaves are really unifolioliate, and are derived from compound leaves. Dahlgren (1988) suggested that the vessel elements have scalariform perforation plates, but they are simple; scalariform pitting is found between vessels and rays. The pits of Ruptiliocarpon are vestured (Mennega 1993).
For information, see Link (1991a: nectaries of Lepidobotrys), Hammel and Zamora (1993: general), Tobe and Hammel (1993: flower and fruit of Ruptiliocarpon), Matthews and Endress (2005b: floral morphology), and Kubitzki (2004b: general), for nodal anatomy of Lepidobotrys, pers. comm. R. A. Howard.
Previous Relationships. Hutchinson (1973) also included Sarcotheca and Dapania (here in Oxalidaceae) with Lepidobotrys, and the leaves of Lepidobotrys are indeed superficially like those of Oxalidaceae, although differing in the stipel and paired stipules. However, the funicular obturator, septicidal capsule, etc., separates Lepidobotrys from Oxalidaceae; furthermore, the sieve tube plastids of Lepidobotrys are the common starch type. Cronquist (1981) included Lepidobotrys in Oxalidaceae, and Takhtajan (1997) placed Leipodoboryaceae and Oxalidaceae alone in his Oxalidales, while suggesting that Ruptiliocarpon - then quite recently described - was rather different, and might even be meliaceous.
CELASTRACEAE R. Brown, nom. cons. Back to Celastrales
Shrubs and trees to lianes (herbs); hexitol dulcitol, flavonols +, ellagic acid 0; tension wood 0 [2 genera]; nodes 1:1; lamina with veins running to congested deciduous tooth; K with a single trace, in bud small, C enveloping flower bud, (fringed); stamens = and opposite K, (staminodes ± fringed); pollen grains often tricellular; G opposite petals, stigma commissural; ovules with parietal tissue 0-1 cell across, laterally thin; exotegmen?.
Age. The age of crown-group Celastraceae in Magallón and Castillo (2009) was ca 71.6 m.y., while Wikström et al. (2001) suggested an age of (88-)85(-82) m.y.; there are similar ages of (89-)76, 71(-60) m.y. in Bell et al. (2010).
Wood attributed to Celastraceae has been found in end-Cretaceous deposits ca 68 m.y.a. in New Mexico (Estrada-Ruiz et al. 2012).
Parnassia et al.
Herbs, perennial or ephemeral; cork?; young stem with separate bundles; petiole bundle arcuate to ± circular; epidermis with tanniniferous cells; leaves spiral, lamina with secondary veins (sub)palmate, stipules 0; inflorescence monochasial or flowers single; K basally connate, quincuncial, 1-trace dividing into 3, (C 0); filament bundle mesarch, staminodes +, complex and fringed, or small, spathulate, opposite petals; nectary at or towards base of staminodes; G [3-4(5)], to ± inferior, odd member abaxial, placentation parietal, stigmas commissural, dry; ovules many/carpel, uni- or bitegmic, (micropyle zig-zag), outer integument 2-3 cells across, inner integument 3-4 cells across, nucellar cap 0?, (endothelium +); (antipodal cells persist); fruit a loculididal capsule; seeds small, exotesta with thickened anticlinal walls, exotegmic cells with ± U-shaped thickening [Parnassia], raphe 0, or endotestal cell walls much thickened, anticlinal walls sinuous [Lepuropetalon], tegmen multiplicative, structure?; endosperm ± 0; n = 9, 16, (23 - Lepuropetalon).
2[list]/51: Parnassia (50). N. temperate to Arctic, Lepuropetalon spathulatum S.E. U.S.A, Mexico, southern South America (map: from Hultén 1971; Fl. China 8. 2001; Alvarez et al. 2013: Parnassia red, Lepuropetalon green). [Photo - Parnassia Flower © H. Wilson.]
Age. The crown-group age of this clade was estimated as (29-)26, 19(-16) m.y. (Wikström et al. 2001) and (48-)34, 28(-17) m.y. (Bell et al. 2010).
Chemistry, Morphology, etc. The single, usually rather large flower of Parnassia is the first flower of a much reduced cyme, and the sessile bract has been interpreted as a petiolate bract the petiole of which is concaulescent with the pedicel (Watari 1939). Staminodes develop later than the stamens, but the androecium is obdiplostemonous. The stamens change their position as they mature, but are initially introrse (Hultgård 1987). The floral anatomy of Parnassia differs from that of Saxifragaceae (Bensel & Palser 1975), where the genus has often been placed. There are conflicting reports on testa anatomy. Lepuropetalon is a very small - and poorly known - plant that may lack a corolla and has simple staminodes, the ovary is more or less inferior and the ovules are unitegmic.
There is other information in Bohm et al. (1986) and Y.-L. Hu et al. (2013), both chemistry, Pace (1912) and Saxena (1976) for embryology, also Murbeck (1918) and Alvarez et al. (2013 and references), both Lepuropetalon, Spongberg (1972: general), Leins (2000: floral morphology of Parnassia), Simmons (2004), and Wu et al. (2005: pollen).
Synonymy: Parnassiaceae Martynov, nom. cons., Lepuropetalaceae Nakai
Shrubs and trees to lianes (herbs); gutta, pyrrolizidine and sesquiterpene alkaloids, distinctive triterpenoids [ß-agarofurans, quinone methides], (maytansinoids - synthesised by associated microorganisms), myricetin +; (cork cortical); true tracheids +; young stem with vascular cylinder; (pericyclic fibres 0); (nodes 3:3 - Brexia; 1:5-7 - Lophopetalum); latex sacs or laticifers +; petiole anatomy often complex; cuticle waxes 0 (platelets); stomata laterocytic (paracytic, etc.), epidermal cork-warts [some Celastroideae]; branching from previous innovation; leaves spiral, opposite, or two-ranked, lamina ptxyis involute (flat-conduplicate), (margins entire; spiny), colleters +, stipules often small (fringed [inc. Brexia]; 0); (2-)4-5-merous; K free or ± connate; A (2-)3-5(-many - Plagiopteron), extrorse, introrse or transverse, (anther slits confluent), (staminodes +, fringed, e.g. Brexia), tapetal cells often multinucleate (binucleate - Stackhousia, Empleuridium); nectary disciform, massive, inside or outside A (0); pollen with endexinal fold in aperture (0); G [2-5(-several)], ± immersed in disc (inferior - A alone on top), when 3 odd member adaxial, (ovary 1-locular), style hollow, (long), stigma not or little expanded; ovules (1-)2-many/carpel, pleurotropous or apotropous (epitropous), apical to basal, (micropyle endostomal), outer integument 3-8 cells across, inner integument 2-4 cells across, (endothelium +), postament +; antipodal cells ephemeral; fruit a (septicidal) capsule, drupe, berry or schizocarp; seeds winged, or with exostomal arils; testa multiplicative, to 16 layers thick (vascularized), exotesta with thick cuticle (tanniniferous), mesotesta with sclerotic cells (0), (exotegmen of laterally compressed fibres; fibres 0; endotegmen persistent, tanniniferous); endosperm copious to 0, embryo green, cotyledons (very) large, (connate); n = 8-10, 12, 14-16, 20, etc.
92/1350: Maytenus (200, inc. Gymnosporia - 70), Salacia (150), Hippocratea (120, inc. Loesenerielle), Euonymus (130), Cassine (60), Crossopetalum (50), Parnassia (50). Largely tropical, but also temperate (map: from Heywood 1978; modified by Hultén & Fries 1986; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010). [Photo - Fruit, Fruit, Collection.]
Synonymy: Brexiaceae Loudon, Canotiaceae Airy Shaw, Chingithamnaceae Handel-Mazzetti, Euonymaceae Berchtold & J. Presl, Hippocrateaceae Jussieu, nom. cons., Plagiopteraceae Airy Shaw, Pottingeriaceae Takhtajan, Salaciaceae Rafinesque, Siphonodontaceae Gagnepain & Tardieu-Blot, nom. cons., Stackhousiaceae R. Brown, nom. cons..
Evolution. Divergence & Distribution. Both Salacioideae and Hippocrateoideae may be Old World in origin (Simmons et al. 2009a, b).
Potential floral synapomorphies for Celastraceae as presently circumscribed are calcium oxalate druses in floral tissues and ovary characters (Matthews & Endress 2005b; Zhang & Simmons 2006).
Ecology & Physiology. Celastraceae are ecologically one of the more important groups of lianes in the New World (Gentry 1991, as Hippocrateaceae).
Seeds of Parnassia are notably small when compared with those of their immediate relatives, possibly associated with the adoption of the herbaceous habit by the genus (Moles et al. 2005a).
Bacterial/Fungal Associations. Some South African Celastraceae have distinctive maytansinoids, ansamycin antibiotics, with a nineteen-member ring (18 C, 1 N), that is likely to be synthesized by the actinomycete Actinosynnema pretiosum, not the plant itself (Pullen et al. 2003; Cassady et al. 2004; Wink 2008).
Chemistry, Morphology, etc. The chemistry of the group would repay further study (see Brüning & Wagner 1978 for a summary). Celastraceae commonly have yellow triterpene derivatives in their bark, and distinctive triterpenoid quinone methides are quite common, although they have not yet been reported from Parnassioideae or from ex-Stackhousiaceae (Gunatilaka 1996; see also Deepa & Narmatha Bai 2010). Monoamine alkaloids such as cathinone and cathine are potentially quite widely distributed in Celastreae (Simmons et al. 2008) and are the active principal in khat, an infusion made from the leaves of Catha edulis. For the identity and biological activity of secondary metabolites of Celastrus, see Su et al. (2009).
The roots of Empleuridium are described as having a superficial cork cambium (Goldblatt et al. 1985). Both Brexia and Parnassia have leaf traces departing from the center of the stem well below the leaf they innervate (Cutler & Gregory 1998).
Polycardia has epiphyllous inflorescences. Savinov (2008) drew the flowers of Stackhousia and Parnassia with the median sepal abaxial. Ex Stackhousiaceae appear to have polysymmetric flowers, but because two stamens are shorter than the others, there is a measure of monosymmetry, too, although I suspect that this is immaterial to the pollinators. A number of taxa have anthers that fall off soon after pollen is dispersed. The filaments are often massive and quite short, and may not be articulated with the anther. Nectary morphology and position - inside or outside of the androecium, vascularized or not, adnate to the gynoecium or not - is notably variable (e.g. Gomes & Lombardi 2013). The flower of Empleuridium has an ovary immersed in the disc and is described as beinovary inferior, although it is clearly superior in fruit; its ovule also has an endostomal micropyle (Goldblatt et al. 1985). The inner integument may be thicker than the outer. Variation in fruit and aril is extensive (Simmons et al. 2001), indeed, Zhang et al. (2012, 2014) suggest that a distinctive feature of arils in Celastraceae is that they develop from the exostome - and so might properly be called caruncles. Salacia has porate pollen; Tripterygium has epitropous ovules. Polyembryony is common in Celastraceae, the embryos developing from the inner integument.
Matthews and Endress (2005b) provide a great deal of information, especially about floral morphology, see also Pierre (1894), Simmons (2004), Savinov (2004) and Leins and Erbar (2010), all general, esp. flowers and fruits. For further details, see Stant (1952: anatomy of Stackhousia), Y.-L. Li and Zhang (1990: wood anatomy), den Hartog and Baas (1978: stomata), Joffily et al. (2010: epidermal cork-warts); see also Andersson (1931), Mauritzon (1933, 1936c, 1939a), Copeland (1967) and Sharma (1968b), all embryology, Klopfer (1973: some floral morphology), Johnston (1975: Canotia), Lobreau-Callen (1977: pollen), Tobe and Raven (1993), and Takhtajan (2000: seed). For general information on Pottingeria, see Airy Shaw et al. (1973), for testa anatomy, see Takhtajan (2000).
Phylogeny. Celastraceae have turned out to be a somewhat problematic group. Some of the initial difficulties encountered in elucidating the phylogeny of the family were because the it was polyphyletic. Thus Bhesa was distinctive in early morphological analyses (Simmons & Hedin 1999), and is now known to be a member of Malpighiales (Zhang & Simmons 2006) as is Goupia (Goupiaceae). Matthews and Endress (2005b) found that Perrottetia was rather unlike other members of the family in characters of floral anatomy, however, that genus has found a firm home in Huerteales near Tapiscia (e.g. M. Simmons in Matthews & Endress 2005b; Worberg et al. 2009). Interestingly, the inclusion of these three genera (and also Siphonodon) in Celastraceae had previously been considered rather uncertain (Metcalfe & Chalk 1950; Ding Hou 1962; den Hartog & Baas 1978; Matthews & Endress 2005b); Siphonodon, however, does not seem about to move. Forsellesia has also moved, in this case to Crossosomataceae (Thorne and Scogin (1978). With the removal of these genera, vessels in Celastraceae are predominantly simple, nodal anatomy unilacunar, stipules are minute, indeed, the family became notably less variable morphologically (Zhang & Simmons 2006).
At the same time Celastraceae are accumulating taxa, that is, some associated families are turning out to be firmly embedded in Celastraceae, and some of the more distinctive groups are briefly characterized at the end of this section. For studies suggesting a broad circumscription of Celastraceae, see also Soltis and Soltis (1997), Savolainen et al. (1997), Zhang & Simmons 2006; etc. More particularly, Stackhousiaceae were included in Celastrales by Takhtajan (1997), but they are consistently embedded in Celastraceae in Savolainen et al. (2000a), Simmons et al. (2000, 2001a, b), Soltis et al. (2007a, but sampling), etc. Ex-Stackhousiaceae are sister to a poorly-supported clade including Maytenus (Coughenour et al. 2010).
Simmons et al. (2000) found Parnassia to group with Celastraceae such as Perrottetia (sic!), although with only moderate support. In Simmons et al. (2001a) [Quetzalia + Zinowiewia] were sister to other Celastraceae s. l. (strong support), then [Perrottetia (again) + Mortonia] were in turn sister to rest of the family (poor support) using PHYB alone; adding morpholology reversed the position of the two basal clades. Zhang and Simmons (2006) could not resolve the relationships between Celastraceae and Parnassiaceae, the latter group being sister to Mortonia and Pottingeria, with parietal placentation, which formed a poorly supported clade very weakly associated with other Celastraceae; Parnassia was monophyletic (100%) and sister to Lepuropetalum (see also Wikström et al. 2001; Soltis et al. 2007a, 2011; etc.). Simmons et al. (2012a), in a study focussing on Euonymeae, found that [Parnassia + Lepuropetalum], [Mortonia + Pottingeria] and [Quetzalia + Microtropis] were successively sister to the rest, but support for these positions was not strong, while in Simmons et al. (2012b) the last two clades reversed their positions.
Brexia, another one-time family segregate, appears to be sister to Empleuridium (Zhang & Simmmons 2006). i>Plagiopteron belongs here; see also Soltis et al. (2007a) who found it was embedded in the family, although sampling was poor. Simmons et al. (2009a) placed it in Hippocrateoideae, while Coughenour et al. (2010) found that it was sister to a clade including ex Salacioideae and Sarawakodendron. Pottingeria, of the monogeneric Pottingeriaceae, is probably also to be included; it is weakly supported as sister to Mortonia (Zhang & Simmons 2006). The xeromorphic Canotia, sometimes segregated in its own family, is close to Euonymus (Coughenour et al. 2010).
Within the old Celastraceae, classical subfamilial limits have not held up at all well. Simmons et al. (2009a) and Coughenour et al. (2010) found that the arillate, capsular Sarawakodendron was sister to Salacioideae, the copious mucilaginous pulp of the berry of that group possibly also being arillate in nature. Sister to this combined group is Hippocrateoideae, with the arillate Helictonema being sister to other taxa (Simmons et al. 2009b; Coughenour et al. 2011). Many Hippocrateoideae have fruits that are deeply trilobed, the lobes being strongly dorsi-ventrally flattened, the seed wings are basal - although some taxa have a corky testa and the wing is vestigial, and the pollen apertures have an annulus (Coughenour et al. 2010, 2011). Sister to the clade made up of all taxa just mentioned is a largely Old-World clade that includes Lophopetaleae. Seed wings in Lophopetaleae vary in their position relative to the body of the seed. For relationships around Maytenus and Gymnosporia, see McKenna et al. (2011). Cassinoideae and Tripterygioideae have turned out to be very polyphyletic (Simmons et al. 2012b). For a phylogeny of Celastrus, see Mu et al. (2012).
Classification. For a reworking of the classification of Celastraceae, we await the conclusion of Mark Simmons's careful march through the family. If [Parnassia + Lepuropetalum] do turn out to be sister to all other Celastraceae, it would be best to recognise two families; although Zhang and Simmons (2006) could not resolve the relationships between Celastraceae and Parnassiaceae, they elected to keep the two families provisionally separate. For generic limits, see Islam et al. (2006), Simmons et al. (2008), and McKenna et al. (2011: the Maytenus and Gymnosporia areas); there are generic problems in Hippocrateoideae (Simmons et al. 2009b) and Salacioideae (Coughenour et al. 2010).
For an account of Stackhousioideae, see Barker (2012).
Previous Relationships. Plagiopteron was included in Flacourtiaceae by Sleumer (1961) and placed in Malvales by Takhtajan (1997). Brexia was included in Hydrangeaceae by Cronquist (1981), but was placed near Celastraceae by Takhtajan (1997). Stackhousiaceae were placed in in Celastrales by both Cronquist (1981) and Takhtajan (1997). Pottingeriaceae were included in Hydrangeales by Takhtajan (1997), who described the stamens as being adnate to the extrastaminal disc, but there is no evidence for such a position. Hippocrateaceae, with A often fewer than C, borne inside/on top of the disc, anthers usu. transversely dehiscent, aril 0, endosperm 0, have often been separated from Celastraceae, but are clearly embedded within them (see above).