EXTANT SEED PLANTS

Plant woody, 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 rich in guaiacyl units; true roots present, apex multicellular, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; 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 mm/mm² [mean for all non-angiosperms 1.8]; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, 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 [N/O//A/C and P//BE lines], 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 in 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 a sieve plate and cytoplasm with P-proteins, companion cells from same mother cell that gave rise to the sieve tube; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable; P not sharply 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, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; 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 four-celled [one-modular, nucleus of egg cell sister to one of the polar nuclei], stylulus short, hollow, stigma ± decurrent, dry [not secretory]; P deciduous in fruit; seed exotestal; 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; 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, minute; 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 + C/PHYB + E gene pairs.

Evolution. Possible apomorphies for flowering plants 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, there is considerable variation between families in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous....

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates, axial parenchyma diffuse or diffuse-in-aggregate; tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

VITALES + ROSIDS: anthers articulated [± dorsifixed, transition to filament narrow, connective thin].

VITALES + ROSIDS: ?

ROSIDS: embryo long; genome duplication; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.

ROSID I/FABIDAE: Endosperm scanty.

FABALES [ROSALES [CUCURBITALES + FAGALES]] - "the nitrogen fixing clade" : (N-fixing by root-dwelling associates [usu. the actinomycete Frankia]); tension wood +; seed exotestal; embryo large.

ROSALES [CUCURBITALES + FAGALES]: 1-2 apical ovules/carpel.

CUCURBITALES + FAGALES: ovary inferior; fruit 1-seeded, indehiscent.

Evolution. "Embryo with large cotyledons" may be another synapomorphy (Zhang et al. 2006), also a three-carpellate gynoecium. However, ovary position and fruit characters in particular reverse spectacularly in this clade (see also Matthews & Endress 2004; Zhang et al. 2006).

CUCURBITALES Dumortier  Main Tree, Synapomorphies.

(Frankia infection via intercellular penetration); ellagic acid ?; storied fusiform cambial initials; perforation plates not or minimally bordered; tension wood?; rays wide, multiseriate; cuticle wax crystalloids 0; leaves spiral, 2ndary veins palmate; K or P valvate, stomata on K/P raised, the two whorls rather similar in texture, micropyle bistomal, styles + [= carpels free immediately above the ovary]. - 7 families, 129 genera, 2295 species.

Evolution. Stem group Cucurbitales originated 107-84 million years ago, crown group divergence began 85-73 million years ago (penalized likelihood dates: Wang et al. 2009).

Butterfly caterpillars may be relatively uncommon on members of the order.

Chemistry, Morphology, etc. Cuticle waxes are usually not well developed. Possession of libriform fibers and slightly oblique end walls of vessel elements may be synapomorphies (Wagstaff & Dawson 2000, see also data in Nandi et al. 1998), as may banded wood parenchyma (Baas et al. 2000), homogeneous rays, and the possession of bitter compounds. Stipules are not placed as a synapomorphy of the order, although given the data presented by Matthews and Endress (2004) that might seem an option; not only do the nature of the stipules in Anisophylleaceae and also Corynocarpaceae need clarification, but presence of stipules may well be a synapomorphy at a much higher level (see above). Zhang and Renner (2003) suggest that the flowers are usually imperfect; flower type varies considerably in Anisophylleaceae, with perfect flowers being known, so that character may properly be placed at a slightly higher level. More or less lacinate petals (and staminodes) are common in the order (Endress & Matthews 2006b). The thickness of the outer integument varies considerably. Matthews and Endress (2004, summarized in 2006b) provide an excellent survey of floral morphology of the group.

Phylogeny. For the circumscription of the clade, rather unexpected as regards families like Coriariaceae and Anisophylleaceae in particular, see e.g. Setoguchi et al. (1999) and Schwarzbach and Ricklefs (2000). Coriariaceae and Corynocarpaceae may be sister taxa, and their wood anatomy is very similar (Carlquist & Miller 2001). However, relationships remained poorly understood (Brouillet 2001 for some comments), although Zhang and Renner (2003a), using a variety of both chloroplast and nuclear genes, suggested that Anisophylleaceae were sister to the rest of the clade. Recently, Zhang et al. (2006) in a nine-gene study (all three compartments) confirm these relationships, and also placed Cucurbitaceae as sister to [Tetramelaceae + Datiscaceae + Begoniaceae], although relationships within this latter group were still not entirely clear, the clade [Datiscaceae + Begoniaceae] having only moderate support (see also Schaefer et al. 2008b; cf. Soltis et al. 2007a). For relationships of Tetramelaceae and Datiscaceae, see Swensen et al. (1994, 1998). The tree here follows that of Zhang et al. (2006) who also discuss aspects of morphological evolution and evaluate the extensive variation in breeding system in the clade. See Matthews and Endress (2004, summary in 2006b) for the floral evolution of the group.

The relationships of the holoparasitic Apodanthaceae are still somewhat unclear. Nickrent et al. (2004) suggested relationships either within Malvales (especially the three-gene analyses and that of nuclear SSU rDNA), or in or near Cucurbitales (analysis of matR.); Barkman et al. (2007: support weak, but rather comprehensive analysis) also suggested the latter position. The mitochondral genes cox1 and matR showed massive divergence, but not the atp1 gene (Barkman et al. 2007). Additional molecular analyses (D. Nickrent, pers. comm.) support the position of Apodanthaceae in Cucurbitales, and this is consistent with their inferior ovary and parietal placentation, both features common in Cucurbitales.

Previous Relationships. Coriariaceae were previously often placed with other families with separate carpels and so thought to be "primitive". Although Rhizophoraceae and Anisophylleaceae were often associated in the twentieth century, e.g. being placed in separate but adjacent orders, as in Takhtajan (1997), or even in the same family, others thought that they were not so close. Thus although both were placed in Rosidae by Cronquist (1981), they were not adjacent. Indeed, morphological differences between the two are marked (e.g. Juncosa and Tomlinson 1988; Tomlinson 1988), and Rhizophoraceae are here placed in Malpighiales, sister to Erythroxylaceae. Similarities in floral morphology between Anisophyllea and Ceratopetalum (Cunoniaceae - Oxalidales: see Matthews et al. 2001; Endress & Matthews 2006b), although striking, are unlikely to be evidence of immediate close relationships of the two families, even although the fossil Platydiscus peltatus seems to suggest similar relationships (Schönenberger et al. 2001a; see also Schönenberger & von Balthazar 2006). Apodanthaceae were often previously included in Rafflesiaceae s.l., Rafflesiaceae s.s. here in Malpighiales.

Includes Anisophylleaceae, Begoniaceae, Coriariaceae, Corynocarpaceae, Cucurbitaceae, Datiscaceae, Tetramelaceae.

Synonymy: Anisophylleales (Bentham & J. D. Hooker) Reveal & Doweld, Begoniales Dumortier, Coriariales Lindley, Corynocarpales Takhtajan, Datiscales Dumortier - Begonianae Doweld, Corynocarpanae Takhtajan, Cucurbitanae Reveal - Coriariopsida Parlatore, Cucurbitopsida Brongniart

ANISOPHYLLEACEAE Ridley   Back to Cucurbitales

Trees and shrubs; plants Al-accumulators; cork?; cambium storying?; nodes 1:1; cuticle waxes as platelets (Polygonanthus - beaker-like); stomata usu. paracytic; branching from current growth, rythmic; leaves (anisophyllous), flat [Anisophyllea], base asymmetrical, (2ndary veins pinnate), margins entire, (stipules 2-4, minute, very base of the petiole [= colleters?]); inflorescence paniculate, racemose or spicate, (plant monoecious); flowers 3-5-merous; K epidermis with mucliaginous inner walls, postgenitally coherent, C open (0), ± enclosing groups of A, lobed or laciniate (entire), bundle number?; A 2x K, (obdiplostemonous), incurved in bud, nectary crenate, inter- and intrastaminal; G [3, 4], 1-2 often unitegmic apotropous ovules/carpel, outer integument 7-8 cells thick, (styles hollow), stigmas expanded; fruit drupe or samara, (K accrescent); testa multiplicative, vascularised or not, 10-30 cells thick; embryo fusiform, largely hypocotylar, cotyledons at most small; n = 7, 8; germination hypogeal.

4[list]/34: Anisophyllea (30). Pantropical (map: see Clement et al. 2004). [Photo - Anisophyllea Fruit]

• Anisophylleaceae are a rather undistinguished-looking family. The plant may be anisophyllous, the leaves being rather coriaceous, often yellowish drying, entire, and often more or less asymmetrical at the base. The flowers are small and the ovary is inferior.

Evolution. Diversification in Anisophylleaceae may have begun (107-)85(-67) million years ago; Combretocarpus is sister to the rest of the family (Zhang et al. 2007).

Chemistry, Morphology, etc. The inner integument is ca 2 cell layers thick, there are no laticifers, the petals are not aristate, and a sclerified exotegmen is absent; in these and other characters Anisophylleaceae differ from Rhizophoraceae (see Juncosa & Tomlinson 1988a, b). The gynoecium lacks a compitum.

For further information, see Vincent and Tomlinson (1983: Anisophyllea architecture), Tobe and Raven (1987c: embryology), Dahlgren (1988), Schönenberger et al. (2001a: fossils), Matthews et al. (2004: floral development), and Zhang et al. (2007: phylogeny).

Previous Relationships. Anisophylleaceae were often linked with or included in Rhizophoraceae (Malpighiales: see above).

Synonymy: Polygonanthaceae Croizat

[Corynocarpaceae + Coriariaceae] [Cucurbitaceae [Tetramelaceae [Datiscaceae + Begoniaceae]]]: uniseriate rays 0; filaments shorter than anthers in bud, anthers basifixed, disc nectaries 0.

Corynocarpaceae + Coriariaceae: ellagic acid +; stomata paracytic; leaf margins entire; flowers small, K quincuncial, C thick, base broad, ovary superior, 1 ovule/carpel, vascular bundle extending into the outer integument; cotyledons very large.

CORYNOCARPACEAE Engler, nom. cons.   Back to Cucurbitales

Trees; young stem with separate bundles; petiole bundles forming line; leaves conduplicate, 2ndary veins pinnate, stipule single, intrapetiolar; inflorescence paniculate; calyx and corolla distinct, C with a single bundle, stamens = opposite and basally adnate to C, incurved in bud, 5 fringed petaloid staminodes with a basal, adaxial staminodial nectary opposite sepals, pollen heteropolar, dicolpate, psilate, infratectum granular; G [?2], transverse?, only 1 fertile, outer integument ca 11[?-30] layers thick, stylulus short, conduplicate, stigma capitate, dry; fruit a drupe, stylodium excentric; seed coat ?pachychalazal, initially thick, vascularised, becoming crushed; endosperm starchy; n = 22, 23.

1[list]/6. New Guinea to New Zealand, introduced on Hawaii (map: from van Steenis & van Balgooy 1966; George 1984). [Photo - Flower] [Photo - Fruit]

• Corynocarpaceae are best recognised by dissecting their flowers. These are quite distinctive, although small: the stamens are opposite the petals and alternate with fringed staminodes, and the ovary has a single style. Vegetatively the family is rather less distinctive, having spirally-arranged leaves with entire margins and intrapetiolar stipules.

Chemistry, Morphology, etc. The plant is very poisonous, having bitter glucosides. The cork develops from the cell layer beneath the epidermis. It is unclear wheteher the gynoecium is pseudomonomerous or unicarpellate, so whether the ovule is apo- or epitropous is unclear. Since variants that have two styles are known (Matthews & Endress 2004), the single, excentrically-placed structure at the apex of the gynoecium is called a stylulus.

Some information is taken from Hemsley (1903: general), Nowicke and Skvarla (1983: pollen) and Philipson (1987a: general).

Previous Relationships. Corynocarpaceae are Celastralean according to Cronquist (1981), isolated, according to Takhtajan (1997), so here they are!

CORIARIACEAE Candolle, nom. cons.   Back to Cucurbitales

Usu. shrubs; roots with N-fixing Frankia; coriolic fatty acid [CH₃(CH₂)₄CH(OH)CH=CHCH=CH(CH₂)₇COOH] in seed, sesquiterpenes, myricetin +; perforation plates bordered; wood with broad rays; nodes 1:1; petiole bundle arcuate; buds usu. perulate; leaves opposite, ± flat, stipules small; plant polygamous or flowers perfect, inflorescences racemes, bracteoles 0; (flowers 6-merous), C open, fleshy, often keeled adaxially; A 10, basifixed, connective thin, pollen (2 colpate), starchy; G [5 (10)], alternate with K, ovule apotropous, micropyle endostomal, both integuments ca 4 calls thick, stylulus slender, stigmatic all around, dry; fruit an achene (nutlet), surrounded by accrescent C; exotesta of cuboid, "tanniniferous", thick-walled, lignified(?) cells, rest undistinguished; n = 10, 15.

1[list]/5. Very disjunct: circum S. Pacific to China and Himalayas, Mediterranean (map: from van Steenis & van Balgooy 1966; Good 1974). [Photo - Inflorescence] [Photo - Fruit]

• Coriariaceae can be recognised by their opposite, sessile, entire leaves with veins coming from the base and at most minute stipules; many branches look like compound leaves, apparently being of limited growth. The inflorescences are racemes and the flowers have a poorly differentiated, biseriate perianth and carpels that are connate at most only basally; the fruits are achenes that are surrounded by the accrescent corolla and have long, subbasal styles that remain attached.

Evolution. Fossils of Coriaria are known from about 33 million years before present (Saporta 1965).

Chemistry, Morphology, etc. Vessels are in multiples, there are true tracheids, and the wood parenchyma is (confluent) vasicentric. Information on nodal anatomy is taken from Sinnott (1914) and that on wood anatomy from Yoda and Suzuki (1992). For gynoecial development, see Guédès (1971).

Phylogeny. For phylogenetic relationships within the family, see Yokoyama et al. (2000); the Eurasian clade is sister to the rest.

Previous relationships. Coriariaceae were placed in Ranunculales by Cronquist (1981) and as a monotypic Coriariales in Rosidae (Takhtajan 1997), largely because of their separate carpels.

Cucurbitaceae [Tetramelaceae [Datiscaceae + Begoniaceae]]: perennial herbs; cucurbitacins [triterpenes] +, myricetin, ellagic acid 0; young stem with separate bundles; leaves with teeth, medial vein ending in a pad of packed translucent cells, lateral also entering [in Begonia lateral is dominant], stipules 0; flowers imperfect; G opposite sepals or median member adaxial, placentation parietal, many ovules/carpel, a roof over the ovary [= styles marginal], stigmas large, elongated, bilobed; seeds many.

Chemistry, Morphology, etc. For information on leaf teeth, see Hickey and Wolfe (1975). The development of a roof over the ovary formed from tissue adaxial to the stylulus (Matthews & Endress 2004) is obvious when well developed; the styluli are then widely separate and borne towards the margin of the ovary. Matthews and Endress (2006) note details of ovule morphology that this group has in common.

CUCURBITACEAE Jussieu, nom. cons.   Back to Cucurbitales

Vines with hypocotylar tubers (lianes; annual herbs), tendrils cauline, ± lateral, both branches and stem coiling; alkaloids, bitter tetra- and pentacyclic triterpenoids, punicic acid [C₁₈H₃₀O₂], citrullin [non-protein amino acid - alpha-amino-delta-ureidopentanoic acid] +, little oxalate accumulation, tannins 0; root cork superficial; stem cork variable in origin; cambium storying?; young stem with separate bicollateral vascular bundles often in two rings; petiole bundle arcuate; no pericyclic sheath; cystoliths frequent; (cuticle waxes as platelets); indumentum rough hairy/prickly, walls calcified, hairs often glandular; leaves often with extrafloral nectaries, (margins entire); plants dioecious (monoecious), inflorescences axillary; flowers ebracteolate or not, (3-)5(-7)-merous, hypanthium + (0; tube formed by adnation of K and C), K often connate, open, (0), C induplicate-valvate, connate, staminate flowers: nectary inside hypanthium; A 5 [Luffa] or fewer, extrorse, variously connate [and forming a central column] or free [and well apart on the hypanthium], anthers monothecal, often much bent and coiled, (locellate), pollen starchy; G 0; carpellate flowers: A rudimentary; G 1 [(2) 3(-5)], inferior, (median member abaxial), nectary on the ovary, hypanthium base as nectariferous trichomes, placentae intrusive, (1-few ovules/carpel), (micropyle endostomal), outer integument 4-5 cells or more thick, (inner integument to ca 6 cells thick - Bryonia, Sechium), nucellar cap or beak +, stigmas dry or wet, (channelled; not bilobed); fruit baccate, often with a thick, hard skin (capsule, ?type); seeds often flattened, pitted, (winged), testa multiplicative, vascularised, often complex, tegmen ± persistent, outer cells ± tracheidal; endosperm 0, chalazal haustorium + (0), cotyledons large; germination epigeal (hypogeal - Momordica).

118[list]/845 - two groups below. Largely tropical and subtropical, especially drier parts of Africa (map: from Heywood 1978 [N. part of range]; Saade 1998; Florabase 2006). [Photos - Collection, Staminate flower, Carpellate flower, Fruit.]

1. "Fevilleoideae" Burnett

Perennials; (tendrils with terminal adhesive pads), axillary bud also present; plant dioecious; staminate flowers: A on or near basal disc [part of hypanthium] formed by nectariferous hairs, pollen grains prolate, to 40 µm long, striate; pistillate flowers: ovules pendulous, styles separate; fruit obconical, opening apically (spherical, ?indehiscent); (seeds winged); testa with aerenchyma [below epidermis] thick-walled and lignified, but hardly differentiated from the hypodermal layer, inner sclerenchymatous layer with anticlinal divisions, brachysclereidal; n = 11, 14, 16.

18/70. Tropical, especially Old World.

2. Cucurbitoideae Kosteletzky

Often annuals; additional non-protein amino acids +; tendrils complex, branches alone coiled [not Thladianthineae]; staminate inflorescence + carpellate flower + bud + tendril making up axillary complex; plant monoecious, (nectar exuded through stomata); staminate flowers: hypanthium well developed (short), pollen grains ± spherical, 40-70(-200: Cucurbiteae) µm long, reticulate, (colpate and (panto)porate; operculate; echinate); pistillate flowers: style single, whether or not also with short branches; fruit ± fleshy; testa with outer layer ± palisade or cubic, mucilaginous, sclereid layer sharply distinguished from other cells, inner layer usu. one layer, cells thickened, much lignified, elongated or not]; n = 9, 11, 12, 14 (etc.).

111/740: Trichosanthes (100), Cucumis (52), Momordica (45). Tropical to warm temperate.

• Cucurbitaceae are easily recognised. They are vines or lianes with often rather roughly hairy exstipulate leaves that have palmate venation. In the leaf axil there is a usually lateral and branched tendril, a vegetative bud, a flower, or a yet more complex organisation. The plants are dioecious or monoecious, and the flowers have a hypanthium, a often complex androecium made up of twisted, monothecal anthers, and an inferior ovary with parietal placentation. The corolla is often more or less yellow, sometimes red. The seeds are more or less flattened.

Evolution. Schaefer et al. (2008b) suggest that stem Cucurbitaceae are some (69-)63(-61) million years old, i.e. Late Cretaceous, with the current world-wide range of the family being in large part the result of extensive dispersal, Madagascar being colonized an estimated thirteen times and Australia twelve times (the latter currently has only twelve genera and thirty species). Interestingly, the woody Socotran endemic Dendrosicyos is dated to (30-)22(-14) million years, although Socotra itself is only about ten million years old, which suggests that the genus - secondarily woody, of course - was once on the mainland and has since become extinct there (Schaefer et al. 2008b).

Low concentrations of the very bitter cucurbitacins, among the most bitter substances known to humans, elicit a compulsive feeding response from diabotricites beetles, rootworm leaf beetles (Chrysomelidae: Galerucinae: Luperini: see Metcalf et al. 1980; Jolivet & Hawkeswood 1995); see Gillespie et al. (2008) for their phylogeny. 805 of the host plant records of the some 1,500 species of the group are from this family. Adults visit the flowers, feeding on pollen, and sometimes other parts of the plant, from whence they sequester the cucurbitacins (Eben 1999). This capability for feeding on Cucurbitaceae may have evolved independently in Old and New World members, Aulacophorina and Diabroticina respectively (Gillespie et al. 2003), the beetles being attracted by volatiles coming both from flowers and other parts of the plant (Andrews et al. 2007 for references). The beetles sometimes cut leaf veins, so locally interrupting the translocation of cucurbitacins to the leaf tissue and so apparently allowing the insect to eat it (Dussourd & Eisner 1987). However, given that at least some of these beetles will eat cucurbitacin crystals, avoidance of the copious sap produced by Cucurbitaceae is a more likely explanation of this feeding behaviour, the more so that the sap, very rich in P-protein, gels within seconds and would gum up the mouth parts, etc., of the beetles (McCloud et al. 1995). There is a remarkable diversity of larvae of Blepharoneura species (Diptera - Tephritidae [fruit flies]) being discovered in flowers and fruits of neotropical Fevilleoideae like Gurania (Condon et al. 2008). Butterfly caterpillars are not often found on members of this family (Ehrlich & Raven 1964).

Some Cucurbitaceae, notably Momordica and Thladiantha, are oil flowers, Ctenoplectridae bees collecting material from the oil-secreting hairs (Buchmann 1987; Vogel 1990 for details). Squash and gourd bees, some 20 species of the genera Peponapis and Xenoglossa, pollinate only species of Cucurbita. They feed early in the day, even flying in the dark (Hurd et al. 1971), and are attracted by particular floral volatiles, repelled by others, which attract the cucumber beetles, while yet others seem to attract both herbivore and pollinator (Andrews et al. 2007). The bees, restricted to the Americas north of northern Peru, show some species-specific variation in pollen collecting devices (Hurd & Linsley 1964: obviously Cucurbita can be pollinated by a variety of other bees since it is cultivated pretty much world wide).

The tendrils of Cucurbitaceae are part of a branch complex. Often there is a sublateral tendril + bud + slightly lateral flower associated with each leaf, or a tendril + vegetative bud + carpellate flower + staminate inflorescence, all more or less collaterally arranged, etc. Eichler (1875) and Goebel (1932) suggested that the tendrils were prophylls, and in Bryonia dioica paired tendrils occur on the pedicel of an axillary flower. Non-flowering Zanonioideae have tendrils more or less lateral to vegetative axillary buds. When flowering finally begins, tendrils are replaced by flowers, which are more or less adaxial to the axillary bud, which now produces an inflorescence branch which has an internode below the prophyllar leaf that subtends the first flower. Most Cucurbitoideae lack an initial prolonged vegetative period, and the inflorescence branch lacks a basal internode, so the first flower, often carpellate, arises in the leaf axil of the main branch and is subtended by a prophyll; the staminate inflorescence represents the development of this prophyllar bud (Lassnig 1997, for details of branching; axillary structures may be collateral in the vegetative part of the plant, sometimes superposed in the reproductive part). However, Gerrath et al. (2008) found that in Echinocystis lobata tendril, lateral bud, carpellate flower, and staminate inflorescence, were all more or less independent in origin, although the latter two did arise from a common primordium. Joliffieae may be critical in understanding the evolution of the branch-tendril complex. Acanthosicyos has paired thorns at the nodes.

Economic Importance. Cucurbitaceae were particularly important in early agriculture in the Americas, being one of the triumvirate of squash, corn and beans. For discussion of various aspects of the history of cultivation of Lagenaria and Cucurbita in particular, see Teppner (2004). For the domestication of squash (Cucurbita spp., inc. C. moschata and C. agyrosperma) which began ca 10,000 years ago, see Dillehay et al. (2007), Piperno et al. (2009) and Ranere et al. (2009); for phytoliths of the family, see Piperno (2006).

Chemistry, Morphology, etc. Cucurbitaceae produce phytoalexins only with difficulty (Harborne 1999). Raffinose is the main transport carbohydrate (Turgeon & Ayre 2005). Distinctive long-chain fatty acids occur in the seed oils; eleostearic acid, an isomer of punicic acid, is restricted to Joliffieae (Hopkins 1990).

A number of African Cucurbitaceae have swollen stem bases. There are extrafascicular sieve tubes in Cucurbita, but they are inside the ring of "pericyclic" fibres (Blyth 1958 and references). Momordica anigosantha in particular has spectacularly monosymmetric flowers; a number of taxa have long-fringed petals. The petals of the woody, succulent-leaved vine, Xerosicyos, are free; those of Echinocystis and Lagenaria at least have several traces. Most, but not all Cucurbitoideae have a disc-like nectary that may even be covered by a flap of tissue, while the nectary hairs of Fevilleoideae are less localized on the petals (Vogel 1997). When the stamens are connate 2 + 2 + 1, the vascular supply shows evidence of this, although there are differences over the interpretation of the apparently bithecal stamens (e.g. de Wilde & Duyfjes 1999). The pollen grains are polysiphonous, and some Cucurbitoideae-Cucurbiteae have grains up to 200 µm or so long. The carpellate flower may have two rings of rudimentary anthers, while in the staminate flowers a ring of processes may alternate with the stamens. The chalazal haustorium of Sechium edule, at up to 19,000 µm long, is apparently the longest in the family, although others are also quite long; only Santalales have longer embryo sacs (Mikesell 1990; Johri et al. 1992). Seedlings commonly have a peg, a cortical outgrowth on the lower side of the seedling axis at the root-shoot transition (e.g. Klebs 1884 for a list of taxa); I do not know if they have been reported from Fevilleoideae, but they will be an apomorphy at quite a high level. In Cucumis, at least, mitochondria (but not chloroplasts) are transmitted paternally (Havey et al. 1998).

For cork cambium, see Dittmer and Roser (1963), for general information, see Jeffrey (1980), Bates et al. (1990), and Jeffrey and de Wilde (2006), for non-protein amino acids, see Fowden (1990), for seed coat anatomy, Singh and Dathan (1998, 2001) and Teppner (2004), and for embryology, etc., Singh (1970).

Phylogeny. Renner et al. (2002) suggested that Cucurbitoideae were probably monophyletic, with Thladiantha possibly sister to the rest; Fevilleoideae (Zanonioideae) formed an unresolved basal polychotomy. This was largely confirmed by Kocyan et al. (2007), although Indofevillea was sister to other Cucurbitoideae; monophyly of Fevilleoideae was not well suppported, Alsomitra sometimes appearing as sister to Cucurbitoideae. Schaeffer and Renner (2008) also found Fevilleoideae to be paraphyletic and did not recognise the subfamily; it is kept here pending the appearance of the classification proposed by these authors. Indeed, Schaefer et al. (2008b) found a grade of four clades basal to a well-supported Cucurbitoideae, in which Indofevilleeae were well supported as being sister to the rest. This basal grade included Gomphogyneae, with only moderate support, Alsomitra being sister to the rest, a strongly supported Fevilleeae, Zanonieae, with 76% ML bootstrap, and a strongly supported Actinostemmateae; relationships between these clades had no support.

Within Cucurbitoideae, phylogenetic studies suggest that Jeffrey's tribes (Jeffrey 2005) were largely supported, although his subtribes were not (Kocyan et al. 2007). Jobst et al. (1998: ITS) found Benincaseae (Cucurbitoideae) to be polyphyletic; Chung et al. (2003) and Schaefer et al. (2008a, esp. b: Alsomitra in Zanonieae) also looked at relationships within Cucurbitoideae. For smaller-scale studies within Cucurbitoideae, see Ghebretinsae et al. (2007), Wilde and Duyfjes (2006), Renner et al. (2007a) and Schaefer et al. (2008b).

Taxonomy. For a suprageneric classification, albeit outdated, see Jeffrey (2005). There are many small genera in Cucurbitaceae, and generic limits need attention, thus Ghebretinsae et al. (2007) had to adjust the limits of Cucumis; see also Wilde and Duyfjes (2006), Renner et al. (2007a) and Schaefer et al. (2008b).

Previous Relationships. Cucurbitaceae have usually been associated with other families that have parietal placentation, whether placed in Violales (Cronquist 1981) or in a group of small orders placed next to each other in Dilleniidae (Takhtajan 1997).

Synonymy: Bryoniaceae G. Meyer, Cyclantheraceae Lilja, Nhandirobaceae Lestibudois, Zanoniaceae Dumortier

Tetramelaceae [Datiscaceae + Begoniaceae]]: pollen spherical, stigmas elongated; fruit a septicidal capsule [dehiscing apically]; seed with operculum; exotestal cells honeycomb [Clement et al. 2004], inner walls strongly thickened and lignified; cotyledons moderate in size.

Chemistry, Morphology, etc. Tebbitt (2005) suggests that the seeds of this group have a lid, but whether this is a synapomorphy or not is unclear. Seeds of Tetramelaceae are apparently unknown, and Boesewinkel (1984) found that the opercula of Datiscaceae and Begoniaceae were rather different.

TETRAMELACEAE Airy Shaw   Back to Cucurbitales

Trees; tannin 0; (wood fluorescing); (nodes with 2 traces from the lateral gaps); hairs glandular or lepidote; (leaf margins entire); plant dioecious, inflorescence spicate; K 4-8, postgenitally coherent, staminate flowers: C 0, or 6-8 [Octomeles], stamens = and opposite petals, incurved; carpellate flowers: C 0; G [3-8], (disc on top), stigmas undivided, decurrent to clavate; fruit also opening down the sides; seed coat?; n = ca 23.

2[list]/2. Indo-Malesia (map: from van Steenis 1953). [Photo - Tree]

Evolution. Tetrameles wood is known fossil from the Deccan Traps in India ca 70.6-65.5 million years old (Zhang et al. 2007).

Chemistry, Morphology, etc. Octomeles has sclereids; its capsular fruits split into two layers, the outer of which falls off.

Datiscaceae + Begoniaceae: ?

DATISCACEAE Berchtold & J. Presl, nom. cons.   Back to Cucurbitales

Roots with N-fixing Frankia; cambium not storied; medullary bundles +; tannin sacs +; leaves deeply divided to odd-pinnate, conduplicate, 2ndary veins ± pinnate; plant (andro)dioecious, inflorescence fasciculate; P 4-10; staminate flowers: P valvate; A 6-25, outer members opposite P, filaments very short; carpellate flowers: G [3-8], opposite P, integument thickness?, embryo sac bisporic, 8-nucleate; fruit septicidal?; seeds with lid, exotegmic cells large, cuboid; endosperm slight; n = 11.

1/2. W. North America, Crete to India (map: from Liston et al. 1989; Clement et al. 2004). [Photo - Flower, Flowers.]

Chemistry, Morphology, etc. The lid on the seeds of Datisca is not surrounded by a ring of collar cells (Boesewinkel 1984: cf. Begoniaceae). The stamens show no particular relationship to the calyx (Takhtajan 1997). Much information is taken from Davidson (1973, 1976).

BEGONIACEAE Berchtold & J. Presl, nom. cons.   Back to Cucurbitales

Fleshy (scandent; shrubby); tanniniferous, soluble oxalate accumulation; cortical (and medullary) bundles +; vessel elements also with scalariform perforation plates; nodes swollen; petiole bundles annular (central bundles +); no pericyclic sheath; sclereids and uncalcified cystoliths +; stomata anisocytic or with accessory cells in two rings [helicocytic]; hairs diverse, often prominent, flattened, pearl glands +; leaves two-ranked (spiral; opposite), laterally or vertically conduplicate (supervolute-curved [prophylls]), (compound), asymmetrical, (margins entire), stipules large, cauline-extrapetiolar; inflorescence cymose, plants mon(di)oecious, staminate flowers first produced; K petaloid, staminate flowers: A 3-many, centrifugal (connate), basifixed, connective enlarged, pollen colpate; carpellate flowers: placentae large, bilobed [= bilamellate], micropyle zig-zag, endothelium +, stigmas often twisted; seeds with lid and surrounding collar cells; n = 10-21+.

2[list]/1401: Begonia (1400: artificial hybridisation within Begonia has been extensive). Largely tropical (map: from Tebbitt 2005). [Photo - Flower, Fruit] [Photos - Collection]

1. Hillebrandia

Plant tuberous, tubers round; T 10, 2-whorled; G [5], only partly inferior, placentation both axile and parietal; n = ?

1/1: Hillebrandia sandwicensis. Hawaii.

2. Begonia

Plant rhizomatous (tuberous); (carpellate flowers first produced - Symbegonia group); staminate flowers: T in 2s, 2(3)4(-8); carpellate flowers: P (2-)5(-9); G [(1)2-3(-6)], placentation axile to parietal (placentae not bilobed), styles central; capsule dehiscing loculicidally (and septicidally) down sides, often asymmetrically winged, (fruit a berry).

1/1400. Largely tropical.

• Begoniaceae may be recognised by their succulent, herbaceous habit and often two-ranked leaves the blades of which have asymmetrical bases and well developed teeth. The hairs are often large, flattened, or almost setular. The plants are monoecious, the staminate and carpellate flowers often have different numbers of tepals, both stigmas and anthers are bright yellow, and the fruit is often winged.

Evolution. Hillebrandia, from Hawaii, is sister to Begonia as a whole (Clement et al. 2001; Swensen et al. 2001), and its age is estimated at 58.5-45 million years (which causes biogeographical problems: Clement et al. 2004, see American J. Bot. 92(8): errata. 2005); the age for crown group Begonia is 37.3-23.2 million years. Other estimates put diversification of the genus as occuring some time from the Eocene to early Oligocene 45-25 million years ago during a period of global cooling (Goodall-Copestake et al. 2009: analysis comprehensive). Recently, Hughes and Hollingswiorth (2008) have suggested that the dearth of widespread species in Begonia is due in part to the low levels of gene flow found in the few studies on members of the genus that have been carried out and hence for the propensity of divergence in allopatry. Butterfly caterpillars are not often found on Begoniaceae (Ehrlich & Raven 1964).

Staminate flowers of Begoniaceae produce pollen, carpellate flowers usually have no reward, but have bright yellow and anther-like stigmas; deceit polination is probably involved (Schemske et al. 1996). There are a few ornithophilous species with nectaries at the base of the styles in carpellate flowers only, others have no reward at all; various levels of deceit/mimicry are again involved (Vogel 1998b; Renner 2006). Tebbit et al. (2006) looked at the evolution of dispersal mechanisms in the speciose Southeast Asian Begonia; taxa with animal or rain-ballist dispersed predominate in a single clade.

Chemistry, Morphology, etc. The leaf teeth are supplied by several veins. The stigmas are described as being antisepalous (Davidson 1973); any style is at most short. Begoniaceae are unusual among monoecious taxa with cymose inflorescences in that the carpellate flowers are produced only later and the first flowers produced in the inflorescence are staminate, although the derived Symbegonia group shows the reverse arrangement.

Hillebrandia has a number of perhaps plesiomorphic features, and some of the features we think of as being characteristic of Begoniaceae as a whole (style position, fruit dehiscence) may in fact be apomorphies for Begonia alone. There are five small orange inner perianth parts (cf. petals) in Hillebrandia that are very different from the large white outer perianth members (cf. sepals). It has been suggested that the perianth of Begonia is to be compared with the sepals of Hillebrandia (see Gauthier 1959), and also that the petals of Hillebrandia are staminodial (Ronse Decraene & Smets 1990), which they are in colour but not in position. The plesiomorphic tepal number of Begonia may be four in staminate flowers (a single whorl, cf. Garcinia, or two bimerous whorls?) and five in carpellate flowers (Forrest et al. 2005). For floral development, see Charpentier et al. (1989).

Phylogeny. For phylogenetic relationships within Begonia, see Plana et al. (2004), Forrest and Hollingsworth (2003) and Forrest et al. (2005). For sections, etc., see Doorenbos et al. (1998).

Classification. For the species of Begonia, see Smith et al. (1986), Golding and Wasshausen (2002) and Tebbitt (2005: more horticultural).

Previous Relationships. Like Cucurbitaceae, Begoniaceae have usually been associated with the other families that have parietal placentation, whether placed in Violales (Cronquist 1981) or in a group of small orders placed next to each other in Dilleniidae (Takhtajan 1997).

APODANTHACEAE Takhtajan   Back to Cucurbitales

Endophytic root or stem parasites; plant monoecious or dioecious; flowers fairly small; P 2 + 4 + 4 or 3 + 6 + 6, nectary +; staminate flowers: gynostemium +; A synandrial, ca 15?, pollen sacs in 1, 2, or 4 rings, extrorse; pollen tricolpate, (apertures 0 - Berlinianche), psilate, pistillode +; carpellate flowers: staminodes 0; G [4 (5)], ± inferior, carpels opposite inner P, placentation parietal, many straight[?] tenuinucellate ovules/carpel, micropyle bistomal, or none, style very short; fruit baccate; testa thin-walled, exo[?]tegmen massively lignified; endosperm +, embryo undifferentiated; n = 16.

3/23(+): Pilostyles (20)[Photo - Flower]. New World from California and Florida southwards, Mediterranean and S. W. Asia, S. W. Australia and E. Africa (map: from George 1984; Novoa 2005; the Parasitic Plants Website 2004). Also Apodanthes, Berlinianche.

• All genera of Apodanthaceae occur as groups of sessile, rather small flowers along the stems of their hosts; the perianth is more or less spreading and the androecium and gynoecium are conspicuous and mound-like in the middle of the flower.

Evolution. Recorded hosts include Fabaceae (perhaps most common), Salicaceae, Burseraceae, and Meliaceae.

Chemistry, Morphology, etc. The characterisation above is incomplete. There are cushions of hairs on the perianth parts (cf. Malvaceae?); for vesicular cells on apex of disc, see Blarer et al. (2002, 2004). For information, see Harms (1935a: general), Kuijt (1969: general), Takhtajan et al. (1985: pollen), Visser (1981), Blarer et al. (2004: floral morphology) and the Parasitic Plants website (Nickrent 1998 onwards) and also Heide-Jørgensen (2008) - both general.