EXTANT SEED PLANTS

Plant woody, evergreen; nicotinic acid metabolised to trigonelline; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins rich in guaiacyl units; true roots present, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem complex; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; stomata ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral, veins -5(-8) mm/mm²; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores] +, grains mono[ana]sulcate, exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, with cell walls, with many flagellae; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplication, mitochondrial nad1 intron 2 and coxIIi3 intron present.

MAGNOLIOPHYTA

Plant woody, evergreen; lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, cyanogenesis via tyrosine pathway [ANITA grade?], lignins derived from both coniferyl and sinapyl alcohols, containing syringaldehyde [in positive Maüle reaction, syringyl:guaiacyl ratio less 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; stem with 2-layered tunica-corpus construction; wood fibers and wood parenchyma +; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides; tracheids +; sieve tubes eunucleate, with sieve plate, companion cells from same mother cell that gave rise to the tube, the sieve tube with P-proteins; nodes unilacunar; stomata with ends of guard cells level with aperture, paracytic; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, vein endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable, P not differentiated, outer members not enclosing the rest of the bud, smaller than inner members, A many, with a single trace, introrse, filaments stout, anther ± embedded in the filament, tetrasporangiate, dithecal, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther, tapetum glandular, binucleate, microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing, pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, exine columellar, endexine thin, compact, lamellate only in the apertural regions, pollen germinating in less than 3 hours, tube elongated, growing at 80-600 µm/hour, with callose plugs and callose-based walls, penetrating between cells, siphonogamy, penetration of ovules within ca 18 hours, distance to first ovule 1.1.-2.1 mm, nectary 0, G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, [outer integument often largely subdermal in origin, inner integument dermal], micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte ?type, stylulus short, hollow, stigma ± decurrent, wet [secretory]; P deciduous in fruit; seed exotestal; double fertilisation +, endosperm ?diploid, cellular [first division oblique, micropylar end initially with a single large cell, chalazal end more actively dividing], copious, oily and/or proteinaceous, embryo cellular ab initio; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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 PHYA/PHYC gene pairs.

Possible apomorphies are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear, because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied. Furthermore, details of relationships among gymnosperms will affect the level at which some of these characters are pegged.

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates; nucleus of egg cell sister to one of the polar nuclei; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

CELASTRALES [OXALIDALES + MALPIGHIALES] (the COM clade): seed exotegmic, cells fibrous.   Back to Main Tree

A number of Malpighiales, including Linaceae, have a fibrous exotegmen similar to that of Oxalidales. In Celastrales, see the similar exotegmen of Lepidobotryaceae, but not Celastraceae, given the recent departure of Perrottetia to Huerteales and Bhesa to Malpighiales (Zhang & Simmons 2006).

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), etc. Oxalidales (it is probably best to include Huaceae) have been found to be sister to the other two orders in some analyses (e.g. Zhu et al. 2007), but here support weakened when chloroplast genes were added.

CELASTRALES Baskerville   Main Tree, Synapomorphies.

Vessel elements with simple perforation plates; tension wood 0 [2 genera of Celastraceae]; stomata ?; leaf teeth?, stipules +; inflorescence cymose; flowers small, micropyle bistomal; chloroplast infA gene present. - 3(4) families, 94 genera, 1355 species.

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 and have quincuncial calyx aestivation.

Includes Celastraceae, Lepidobotryaceae, Parnassiaceae, Pottingeriaceae.

Synonymy: Brexiales Lindley, Parnassiales Nakai - Celastranae Takhtajan - CelastropsidaBrongniart

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).

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, articulated with petiole, 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], 2 collateral apical pachychalazal epitropous ovules/carpel, outer integument 7-10 cells across, inner integument ca 4 cells across [Ruptiliocarpon], funicular obturator +, styles ± separate, stigmas capitate or style short, stigma lobed; fruit a septicidal capsule, endocarp distinct, columella persisting; seed arillate, integuments multiplicative, exotegmic cells fibrous, strongly thickened, other cells ± crushed (not fibrous - Lepidobotrys); endosperm 0; n = ?

2[list]/2-3. E. Africa (Lepidobotrys staudtii), Central and South America, scattered, to Peru (Ruptiliocarpon caracolito) (Map: from Hammel & Zamora 1993; Heywood 2007). [Photo - Fruit]

• Lepidobotryaceae may be recognised by their entire, simple but articulated leaves with both stipules and stipels. The inflorescence often seems to be opposite the leaves because it is evicted by the growth of a robust axillary shoot. The flowers are small, with free sepals and petals and ten basally-connate stamens; the antepetalous stamens have longer filaments than the antesepalous whorl. The mesocarp, with its distinctive ladder-like fibers arranged radially, separates from the horny endocarp.

There is no evidence other than morphology (articulation, stipels) that the apparently simply leaves are really unifoliate, 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).

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. Takhtajan (1997) suggested Ruptiliocarpon might be meliaceous.

For information, see Link (1991a: nectaries of Lepidobotrys), Hammel and Zamora (1993: general), Tobe and Hammel (1993: flower and fruit of Ruptiliocarpon), and Kubitzki (2004b: general), for nodal anatomy of Lepidobotrys, pers. comm. R. A. Howard.

CELASTRACEAE R. Brown, nom. cons.   Back to Celastrales

Shrubs and trees to lianes (herbs);hexitol dulcitol, flavonols +, ellagic acid 0; nodes 1:1; leaves with veins running to congested deciduous tooth; sepals with a single trace, stamens = C, pollen often trinucleate, G opposite petals, ovules ± tenuinucellate, stigma commissural; exotegmen?.

92[list]/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; Hultén & Fries 1986). [Photo - Fruit, Fruit, Collection]

Both Brexia and Parnassia have leaf traces departing from the center of the stem well below the leaf they innervate (Cutler & Gregory 1998). The petals protect the flower when in bud, not the sepals; Endress and Matthews (2006b) illustrate fringed petals, staminodes, etc. A number of taxa have anthers that fall off soon after pollen is dispersed.

Simmons et al. (2000) found Parnassia to group with Celastraceae such as Perrottetia (this is now in Huerteales...), although with only moderate support; more mergers may yet be in order. In Simmons et al. (2001a) Quetzalia and Zinowiewia were a clade sister to rest of Celastraceae s. l. (strong support), then Perrottetia (again!) and Mortonia were sister, in turn sister to rest of the family (poor support) using PHYB alone, but adding morpholology reversed the position of the two basal clades - Parnassia was not included. Zhang and Simmons (2006) could not resolve the relationships between Celastraceae and Parnassiaceae and elected to keep them provisionally separate; Parnassia seemed to be monophyletic and sister to Lepuropetalum. It is possible that Parnassiaceae should be part of a broadly-circumscribed Celastraceae; Parnassia, along with Mortonia and Perrottetia, are in a clade sister to the rest (e.g. Simmons et al. 2001b).

Matthews and Endress (2005b) provide a great deal of information about this clade.

PARNASSIACEAE Martynov, nom. cons.   Back to Celastrales

Herbs; cork?; young stem with separate bundles; petiole bundle arcuate to ± circular; epidermis with tanniniferous cells; leaves spiral, 2ndary veins (sub)palmate, stipules 0; inflorescence monochasial or flowers single; K basally connate, C 0, 5, stamens = and opposite sepals, staminodes often complex, opposite petals, nectar at or towards base, G [3-4(5)], to ± inferior, odd member abaxial, placentation parietal, many uni- or bitegmic ovules/carpel, nucellar cap 0?, stigmas dry; fruit a capsule; seeds small, exotesta with thickened anticlinal walls, exotegmic cells with ± U-shaped thickening [Parnassia], raphe 0, or endotestal cell walls much thickened [Lepuropetalon], endosperm ± 0; n = 8, 9, 23.

2[list]/51: Parnassia (50). N. temperate to Arctic, Lepuropetalon spathulatum, S.E. U.S.A to Mexico, Chile (Map: from Hultén 1971). [Photo - Parnassia Flower © H. Wilson]

• Parnassiaceae are herbs that may be recognised by their serrate leaves that often have reddish lines or dots when dry. The flowers are radially symmetrical, petals, when present, are free, there are only five stamens, and the ovary has parietal placentation. There are five staminodes, those of Parnassia being large and particularly distinctive.

Seeds or Parnassiaceae are notably small when compared with those of their immediate relatives, possibly associated with the adoption of the herbaceous habit by the clade (Moles et al. 20005a).

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.

See also information in Bohm et al. (1986: chemistry), Murbeck (1918: Lepuropetalon), Spongberg (1972: general), Leins (2000: floral morphology of Parnassia), Simmons (2004), and Wu et al. (2005: pollen).

Synonymy: Lepuropetalaceae Nakai (plant very small; C 0, staminodes alternate with K, not elaborated, G ± inferior, ovules unitegmic; n = 23).

Shrubs and trees to lianes (herbs); gutta, pyrrolizidine and sesquiterpene alkaloids, distinctive triterpenoids [quinonemethides], (maytansinoids - synthesised by associated microorganisms), myricetin +; (cork cortical); true tracheids +; young stem with vascular cylinder; (nodes 3:3 - Brexia; 1:5-7 - Lophopetalum); latex sacs or laticifers +; petiole anatomy often complex; cuticle waxes 0 (platelets); (stomata laterocytic); branching from previous innovation; leaves spiral, opposite, or two-ranked, 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, borne inside or outside prominent disc (disc 0), (slits confluent), tapetal cells often multinucleate (binucleate - Stackhousia), pollen with endexinal fold in aperture (0), G [2-5(-several)], ± immersed in disc (inferior - A alone on top), when 3 odd member adaxial, (1-)2-many apotropous apical-basal ovules/carpel, (micropyle endostomal), endothelium +, style hollow, (long), stigma not or little expanded; fruit a (septicidal) capsule, drupe, berry or schizocarp; seeds winged, or with exostomal, hilar or funicular arils; testa multiplicative, to 16 layers thick (vascularised); exotesta with thick cuticle (tanniniferous), mesotesta with sclerotic cells (0), (exotegmen of tall lignified fibers - Zinowiewia; endotegmen persistent, tanniniferous); endosperm copious to 0, embryo green, cotyledons (very) large, (connate); n = 8-10, 12, 14-16, 20, etc.

• The family is vegetatively variable - Microtropis may have oppposite, entire, exstipulate leaves, while spiral and opposite leaves on the one plant are not infrequent, as in Catha and Salacia. However, opposite, serrate leaves are common and the stipules are small and quite often fringed; strongly ascending veins are prominent on dried specimens. Thin, spiral threads are often evident when the lamina is torn transversely. The inflorescences are often cymose, and the flowers, with their usually very broad disc in which the ovary is more or less immersed and five or fewer stamens, are often distinctive. The fruit varies greatly, but it is frequently a loculicidal capsule with winged or arillate seeds. The colleters may turn black, as in Paxistima.

Polycardia has epiphyllous inflorescences. The flower of Empleuridium has an ovary immersed in the disc that is described as being inferior; it is superior in fruit. Its ovule also has an endostomal micropyle. Filaments in Celastraceae, at least, are often massive, and may not be articulated with the anther. Polyembryony is common in Celastraceae, the embryos developing from the inner integument. The inner integument may be thicker than the outer. Variation in fruit and aril is extensive (Simmons et al. 2001). Salacia has porate pollen; Tripterygium has epitropous ovules.

Brexia was included in Hydrangeaceae by Cronquist (1981), but was placed near Celastraceae by Takhtajan (1997). Details of its anatomy may be found in Ramamonjiarisoa (1980), who notes its similarity to that of Celastraceae; for nodes, see Swamy (1964). The ovules are bistomal and crassinucellate (e.g. Hils 1985). Bensel and Palser (1975) noted that both Brexiaceae and Celastraceae have dulcitol; they suggested that the androecium in Brexiaceae is derived from an ancestor that was fasciculate; this is perhaps unlikely. Exotegmic cells are of the hour-glass type, and other cells are much thickened, but testa anatomy of Brexia and Celastraceae s. str. is similar, although its integuments are multiplicative. Brexia appears to be sister to Empleuridium (Zhang & Simmmons 2006)

Bhesa is distinctive in morphological analyses (Simmons & Hedin 1999), and is apparently a member of Malpighiales (Zhang & Simmons 2006); Perrottetia has found a home in Huerteales near Tapiscia (M. Simmons in Matthews & Endress 2005b). Interestingly, the inclusion of both these genera (and also Siphonodon) in Celastraceae has been uncertain (Metcalfe & Chalk 1950; Ding Hou 1962; Matthews & Endress 2005b); Siphonodon, however, does not seem about to move. With the removal of these two genera, vessels in Celastraceae are predominantly simple, indeed, the family is now notably less variable morphologically (Zhang & Simmons 2006). Forsellesia has also moved, in this case to Crossosomataceae (Thorne and Scogin (1978).

At the same time, Celastraceae are accumulating taxa. Stackhousiaceae were included in Celastrales by Takhtajan (1997); they are embedded in Celastraceae in Savolainen et al. (2000a) and Simmons et al. (2000, 2001a, b). For studies suggesting a broad circumscription of Celastraceae, see also Soltis and Soltis (1997), Savolainen et al. (1997), Zhang & Simmons 2006; etc.; see above for the possible inclusion of Parnassiaceae. Pottingeria, of the monogeneric Pottingeriaceae, is probably also to be included; it is weakly supported as sister to Mortonia (Zhang & Simmons 2006). Here it is kept separate pending a more detailed study of Celastraceae s.l. Potential synapomorphies for Celastraceae as presently circumscribed are calcium oxalate druses in floral tissues and ovary characters (Matthews & Endress 2005; Zhang & Simmons 2006). For generic limits, see Islam et al. (2006) and Simmons et al. (2008).

The chemistry of the group would repay further study. Celastraceae commonly have yellow triterpene derivatives in their bark. Distinctive triterpenoid quinone methides are quite common in Celastraceae, although they have not been reported from Parnassiaceae nor from ex-Stackhousiaceae (Gunatilaka 1996). Monoamine alkaloids such as cathinone and cathine are potentially quite widely distributed in Celastreae (Simmons et al. 2008) and are of course the active principal in khat (from Catha edulis); for maytansinoids (South African), see Pullen et al. (2003).

Plagiopteron belongs here (see also Soltis et al. 2007: embedded in the family); see Baas et al. (1979) for a discussion on the nature of the perianth in the genus, Tang (1994) for its embryology. The epidermal cells of the lamina are crystalliferous, and the thin-walled, unlignified fibres contain elastic material, as in some other Celastraceae (Takhtajan [1997] described the plant as having latex canals). The pollen has smooth exine, a collared ectopore and thickened endexine bordering the endopore - rather unlike other Celastraceae. Plagiopteron was included in Flacourtiaceae by Sleumer (1961) and placed in Malvales by Takhtajan (1997).

Nicobariodendron is only doubtfully included here by Simmons (2004). It has mucilage cells, distichous (opposite - Simmons 2004) exstipulate leaves, axillary, racemose inflorescences, the plant is dioecious, the flowers are small, the staminate flowers having only two stamens borne outside the disc and a central pistillode, and the fruit is a drupe with a single, basal seed and persistent calyx (Vasudeva Rao & Chakrabarty 1985).

For further details on morphology, see Pierre (1894: general), Johnston (1975), Li and Zhang (1990), Tobe and Raven (1993), Takhtajan (2000), Savinov (2004: floral morphology) and Simmons (2004: general).

Synonymy: Brexiaceae Loudon (leaves conduplicate; disc with stiff processes; exotestal cells tanniniferous, outer wall thickened, with transverse thickenings in surface view, endosperm thin; n = 30, 32), Canotiaceae Airy Shaw (leaves minute, distinctive axillary black glandular patches; inflorescence fasciculate; 2-6 tenuinucellate ovules/carpel; fruit an initially septicidal capsule, then carpel units opening adaxially, or 1-seeded drupe; exotesta tanniniferous, thick-walled or not, exotegmen tracheoidal), Chingithamnaceae Handel-Mazetti, Euonymaceae Berchtold & J. Presl, Hippocrateaceae Jussieu (A often fewer than C, borne inside/on top of the disc, anthers usu. transversely dehiscent, aril 0, endosperm 0), Plagiopteraceae Airy Shaw (liane; indumentum stellate; stomata anomo- or cyclocytic; leaf margins entire, stipules minute; inflorescence axillary, paniculate; epicalyx (2-)4(-5), subulate, K (3) 4 (5), valvate, C 0, A numerous, filaments expanding apically and anthers opening by confluent apical slits, nectary 0?, G [3], 2 erect weakly crassinucellate apotropous ovules/carpel, micropyle zig-zag, endothelium +, style +, stigma punctate; fruit winged, septicidal; testa?), Salaciaceae Rafinesque, Siphonodontaceae (Croizat) Tardieu-Blot, Stackhousiaceae R. Brown, nom. cons. (rhizomatous, ± herbaceous (annual); flowers rather small; hypanthium +, lined by nectary, K small, C clawed, limbs connate or not, A 3 + 2 shorter, G [2 (3-5)], 1 erect ovule/carpel, micropyle exostomal, style or styles +, stigmas elongate, commissural; fruit a dry schizocarp; exotesta with tangentially-elongated tanniniferous cells, tegmen absorbed; endosperm +; n = 9, 10, 15).

POTTINGERIACEAE Takhtajan   Back to Celastrales

Evergreen tree; vessel elements with scalariform perforation plates [young stem]; nodes 1:1; leaves spiral, margins entire, 2ndary venation palmate, stipules minute, cauline; inflorescence fasciculate; flowers small, K and C free, stamens = and opposite sepals, borne near outside and on undersurface of a large disc, G [3], placentation intrusive parietal, many ovules/carpel, style +, short, styles relatively long, spreading; fruit a septicidal capsule, A and placental bundles persistent; mesotesta fibrous; endosperm copious; n = ?

1/1: Pottingeria. Assam to N.W. Thailand.

The plant dries pale) brown.

No characters obviously link Pottingeria with any other group, although it is obviously not very different from Celastraceae. Indeed, Pottingeria was placed in Celastraceae subfamily Pottingerioideae by Airy Shaw (in Airy Shaw et al. 1973), and this is consistent both with nodal and testa anatomy. 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.

For general information, see Airy Shaw et al. (1973), for testa anatomy, see Takhtajan (2000).