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].

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" :   Back to Main Tree
(N-fixing by root-dwelling associates [usu. the actinomycete Frankia]); tension wood +; seed exotestal; embryo large.

Evolution. There are at least six independent establishments of symbioses with Frankia, a gram-positive actinomycete, in this clade that result in the plant being able to fix nitrogen, and at least two more associations with rhizobia (e.g. Swensen 1996; Clawson et al. 2004). Although there is considerable variation in morphology of the nodules, it does not correlate with bacterium type. In Fabaceae the nodules arise from the cortex and have peripheral vascular tissue with bacterial infected cells in the center, while in all other nodules, whether associated with Frankia or rhizobia, the nodules are modified lateral roots. There the vascular tissue is central, initiation of the nodule is pericyclic, and it is the cortical cells that contain bacteria (Gualtieri & Bisseling 2000; Vessey et al. 2004).

Jeong et al. (1999) and Clawson et al. (2004) compare the phylogenetic relationships within Frankia with those of its hosts; Clawson et al. (2004) suggest that all the three clades of Frankia that they recognise may have diverged before the evolution of the angiosperms. Intercellular penetration of the root epidermis may be the plesiomorphic route of infection, occuring in both Rosales and Cucurbitales; in Fagales infection is by root hairs (Clawson et al. 2004). However, given the absence of strong phylogenetic structure in the group, details of how infection patterns map on to phylogeny are unclear (see also Soltis et al. 2005a). The situation is yet more complex. In Mimosa and some Faboideae, at least, ß-proteobacteria like Burkholderia phymatum also form nodules that may effectively fix nitrogen, while the α-proteobacteria that form nodules in other Fabaceae occur in four separate clades (Moulin et al. 2001; Sprent 2002; Elliott et al. 2007). It has been found that there is a relatively small "symbiosis island" that may be exchanged among bacteria and that enables nodulation to develop (Sullivan & Ronson 1998). Haemoglobin is intimately involved in helping preserve the largely oxygen free micro-environment the bacteria need for nitrogen fixation; a variety of haemoglobins are involved, including haemoglobin synthesized by Frankia (Vessey et al. 2004).

Nitrogen fixation in this group of four orders is a classic example of a "tendency" or a predisposition (Vessey et al. 2004), but the possible molecular reasons for the restriction of these diverse bacterial associations to the N-fixing clade are now being dissected. A number of the genes involved in both the actinomycete and Rhizobium symbiosis are the same as those involved in establishing vesicular-arbuscular mycorrhizal associations. One of these genes, the symbiosis receptor kinase gene, exists in a particularly distinctive form in the N-fixing clade - and also in Tropaeolum, but not rice, tomato or poppy. This gene in the latter genera could rescue mycorrhizal formation in defective forms of the gene in Fabaceae, but not nodule formation, whereas the Tropaeolum gene could restore the ability to form nodules (Markmann et al. 2008; see also Chen et al. 2007; Gherbi et al. 2008; Yano et al. 2008; Markmann & Parniske 2009). Perhaps connected (in some way) with nitrogen fixation is the fact that taxa scattered in the nitrogen-fixing clade may form root clusters of varying morphologies; in some cases, at least, these have been shown to facilitate phosphorus uptake in phosphorus-poor soils (Lambers et al. 2006).

There may be associations of this clade with particular butterflies (as food sources), and within Fabales and Rosales in particular (Ackery 1988, 1991). Indeed, it has been suggested, as by Scott (1985) and Janz and Nylin (1998; see also Braby & Trueman 2006) that the ancestral food plant for caterpillars of butterflies as a whole may have been Fabales (but note that caterpillars are common only on Fabaceae) or perhaps in the rosid I group; Ackery (1991) also suggested Malvales as a possibility. Rosids as a whole are another possibility (e.g. Powell 1980; Berenbaum & Passoa 1999).

Phylogeny. For the limits of the N-fixing clade, a rather unexpected group, see Chase et al. (1993, 1999), Savolainen et al. (1997), Soltis et al. (1995b, 1997, 1998), and Swensen (1996). Although it is not recovered by some analyses in the complete chloroplast genome study of Bausher et al. (2006), the poor sampling - no other rosid I taxa were included - may well be reponsible. The clade had little support in the mitochondrial matR analysis of Zhu et al. (2007), but support was much strengthened when two chloroplast genes were added. Relationships within the clade have been unclear, and Zhu et al. (2007) could not even recover a monophyletic Rosales using the mitochondrial matR gene; the other three orders were, however, all strongly supported. Sytsma et al. (2002) recovered a topology [Cucurbitales [Fabales [Fagales + Rosales]]], while in Zhu et al. (2007: four genes) the position of the first two was reversed, albeit in both studies there was little support for the topologies found. However, Ravi et al. (2007) examining data sets including 61 protein-coding genes (only three of the orders) and four genes (Fagales, the missing order, included) found good support for [Fabales + Rosales] and some support for the broader grouping [Cucurbitales [Fagales [Fabales + Rosales]]]. Apart from Fabales (three Fabaceae-Faboideae included), the other orders were represented by single exemplars. A [Fabales + Rosales] clade was also obtained by Jansen et al. (2007) and Moore et al. (2007), but no Fagales were included in these studies. In other analyses there is some support for a [Cucurbitales + Fagales] clade (see Chase et al. 1993; Setoguchi et al. 1999; Schwarzbach & Ricklefs 2000; Soltis et al. 2000, 2003a; Zhang et al. 2006). The support for the topology in the Summary Tree is quite strong (Moore et al. 2008; ), but confirmation after e.g. increased taxon sampling would be comforting.

FABALES Bromhead  Main Tree, Synapomorphies.

Ellagic acid 0; wood often fluorescing; nodes?; styloids +; carpels free, embryo green. - 4 families, 754 genera, 20055 species.

Evolution. Fabales contain ca 9.6% eudicot diversity (Magallón et al. 1999), of which the bulk is made up of Fabaceae. Wikström et al. (2001) date the origin of the clade to 94-89 million years before present, diversification beginning 79-74 million years before present - although Fabaceae themselves, which contain the bulk of the species in the oder, may not have begun diversifying for another twenty million years or so. Wang et al. (2009) dated stem group Fabales (109-)104(-99) or (92-)89(-86) million years ago and crown group Fabales (90-)87(-84) or (75-)72(-69) million years ago, depending on the analysis.

Chemistry, Morphology, etc. The distribution of a number of features may be of systematic significance in this clade, but sampling is poor; the problem is compounded by the uncertain phylogenetic relationships within Fabales. Note the variation in nodal anatomy within the order; variation within Surianaceae is correlated with presence/absence of stipules. Although styloids are reported from Surianaceae, Quillajaceae and Fabaceae, details of their distribution within Fabaceae are unclear; they are certainly quite common in Faboideae (Lersten & Horner 2005), apparently less so in the rest of the family. Despite the floral differences between Polygalaceae and Fabaceae, there are some developmental similarities between the two (Prenner 2004d). The rpl22 gene is in the nucleus in Polygalaceae and Fabaceae (i.e. is absent from the chloroplast), but the condition in the rest of the order is unknown (J. J. Doyle et al. 1995). Some distinctive palynological features are scattered here: Quillajaceae and some Surianaceae have exine protruding at the apertures, and these and Fabaceae-Cercideae (although perhaps derived within that group?) have striate pollen (Banks et al. 2003; Claxton et al. 2005). It would be nice to know if Surianaceae or Quillajaceae had starchy endosperm, and more details of their chemistry are needed. Many Fabaceae-Faboideae have lost the rps16 gene, and it is also absent from Polygala (Downie & Palmer 1992: but again, sampling).

Phylogeny.Fabales were a rather unexpected group, but it is quite strongly supported - see Morgan et al. (1994), Källersjö et al. (1998), etc., however, Hilu et al. (2003) found Larrea (Zygophyllaceae) to be weakly associated with Fabaceae, the only member of Fabales included in their rbcL analysis. Persson (2001) suggested the relationships [Polygalaceae [Surianaceae [Quillajaceae + Fabaceae]]], but there was little support for this (see the tree in versions 1-7). Forest et al. (2002) found weak support for the topology [Quillajaceae [Fabaceae [Surianaceae + Polygalaceae]]], and Banks et al. (2008) suggest that there is strong support for the relationship [Quillajaceae [the rest]] (see the tree here), although Wojciechowski et al. (2004, but sampling) suggested the possibility of a [Surianaceae + Quillajaceae] grouping... The unrooted topology in Bruneau et al. (2008a) is [Polygalaceae [Quillajaceae + Surianaceae] Fabaceae]. Bello et al. (2009) in a careful analysis on matK and rbcL data, preferred relationships obtained in a maximum parsimony analysis of [[Polygalaceae [Fabaceae [Surianaceae + Quillajaceae]]], however, support was poor - and if anything still poorer for any relationships obtained in Bayesian analyses of the same data. Wang et al. (2009) did not obtain well supported relationships in this clade in their twelve gene analysis of the rosids.

Includes Fabaceae, Polygalaceae, Quillajaceae, Surianaceae.

Synonymy: Caesalpiniales R. Brown, Cassiales Horaninow, Polygalales Dumortier, Quillajales Doweld, Surianales Doweld - Fabanae Reveal, Polygalanae Doweld - Polygalopsida Endlicher

QUILLAJACEAE D. Don   Back to Fabales

Small evergreen tree; saponins, proanthodelphinidin, flavone C-glycosides +; storying?; nodes 1:3; petiole bundles arcuate, no pericyclic fibers; hairs warty, leaves spiral, conduplicate, margins toothed [hydathodal?], stipules petiolar; inflorescence terminal, cymose; hypanthium +, K valvate, nectary on lower half of K, C contorted, spathulate, clawed; A 5 opposite sepals above nectary + 5 opposite C below nectary, pollen striate; G becoming [5], opposite sepals, ?micropyle, several pleurotropous ovules in two marginal rows/carpel, stigmatic zone elongated along styles; fruit strongly asymmetrically lobed, follicular, opening down both surfaces of the lobes, K moderately accrescent; seeds winged, 3 outer testa layers thickened, sclerotic, tegmen disintegrating; endosperm type?, cotyledons investing radicle, conduplicate; n = 14, 17.

1/3. Temperate South America (map: from Donoso Z. 1994; Culham 2007). [Photo - Flower, Fruit.]

• Quillajaceae are vegetatively rather undistinguished with their spiral, serrate, stipulate leaves, although the conspicuous teeth appear to be hydathodal. They may be readily recognised by their remarkable flowers in which the antesepalous stamens are borne on the outer edge of the disc some way up the sepals and the antepetalous stamens are near the base of the ovary. The petals are clawed and the strongly lobed fruits open down both the inner and outer surfaces of the lobes and contain winged seeds.

Chemistry, Morphology, etc. The leaves are amphistomatous. The flowers of Quillajaceae, with their distinctive positioning of nectary and androecium, may be interpreted as having a hypanthium. Development of the androecium is unidirectional and is rather like that of Fabaceae (Bello et al. 2007/8). The carpels are definitely connate axially, but are largely free laterally, cf. earlier versions of this site. There appear to be only three traces to each carpel, although Sterling (1969) noted that there were also "intermediate" bundles. Robertson (1974) noted that n = 17.

See also Hegnauer (1973, 1990, as Rosaceae) for chemistry, Sterling (1969) and Kania (1973) for gynoecial morphology, Lersten and Horner (2005) for vegetative anatomy, particularly styloids, Kubitzki (2006b) for a general account, and Bello et al. (2007, reprinted 2008) for floral development. Additional data from: Aronson 7897 (anatomy, embryo).

Previous Relationships. Quillaja was included in Rosaceae as part of Quillajoideae (Takhtajan 1997) or, more usually, it has been included in Spiraeaoideae, e.g. as Quillajeae (Robertson 1974). It is indeed superficially quite similar to the South American Kageneckia, but wood anatomical data, etc., suggest that it should be removed from Rosaceae (Lotova & Timonin 1999; cf. Zhang 1992).

Fabaceae [Surianaceae + Polygalaceae]: ?

FABACEAE Lindley, nom. cons.//LEGUMINOSAE Jussieu, nom. cons. et nom. alt.   Back to Fabales

Trees to annual herbs; lectins [haemagglutinins] and gums esp. in seeds, 5-deoxyflavonoids, Cglycosylflavonoids, pinitol [cyclitol] +; cork also in outer cortex; cambium storied; secretory cells common, sieve tube plastids with protein crystals (and/or starch, or simply starch); nodes 3:3; cuticle wax platelets as rosettes; stomata various; branching from previous flush; colleters +, hairs often uniseriate (mesifixed); leaves (opposite), pari- or odd-pinnately compound (palmate, simple), leaflets often pulvinate, (glandular-punctate), stipellate or not, opposite (alternate), conduplicate, (margins lobed, toothed; 2ndary veins palmate); inflorescence racemose; flowers (3-)5(-6)-merous, floral developmental sequence K-G-C-outer whorl A-inner whorl A [G initiation/development much advanced], hypanthium +, K initiation helical, C clawed, adaxial-median member internal [descending cochleate], A (2-)10(-many); G 1, stipitate, several serial ovules/carpel, chalazal embryo haustorium +, micropyle zig-zag, styles long, (hollow), stigma expanded or not, wet; fruit follicular, dehiscing abaxially also; exotesta palisade, linea lucida separating much thickened outer anticlinal walls from the thinner inner walls, pleurogram [area of cells with a deep-seated linea lucida] + (0), linea fissura [fine line delimiting pleurogram] ± circular/oval [closed], (0), mesotesta of stellate cells, (seed coat undistinguished), tegmen crushed; (thick-walled endosperm with galactomannans [Schleimendosperm]), chalazal endosperm/suspensor haustoria + [?level]; cotyledons investing radicle; rpl22 gene absent.

730/19400 - discussed in six groups below. World-wide.

1a. Cercideae

Trees to lianes; leaves apparently simple, bilobed or not; pollen striate, funicle?; n = 7, etc.

4-12/265: Bauhinia (250). Pantropical (temperate) (map: from Meusel et al. 1965; Sales & Hedge 1996). [Photo - Bauhinia]; [Photo - © D. Kimbler - Cercis]

Synonymy: Bauhiniaceae Martynov

1b. Duparquetia

Leaves once-compound; floral development acropetal ["normal"], K 4, petaloid, adaxial-median C external; A 4, opposite K, connate, porate, pollen asymmetrical, ectoaperture encircling the equator, with two endoapertures; G initiation not advanced.

1/1: Duparquetia orchidacea. Tropical W. Africa.

1c. Detarieae

Resins with bicyclic diterpenes; leaf phloem transfer cells; leaflets with crater-like glands on the abaxial surface, stipules deciduous, intrapetiolar; bracetoles well developed, deciduous; (pollen striate); endosperm 0, amyloid and xyloglucans in cotyledon cell walls; x = 12.

"Caesalpinioideae" + Mimosoideae + Faboideae: (N-fixation); (non-protein amino acids, esp. in seeds, +); vestured pits + (0); (fruit a drupe, samara, schizocarp, etc.).

2. "Caesalpinioideae" Candolle

Shrubs or trees (herbs); (N-fixing, rhizobia remain in infection threads), often with ectotrophic mycorrhizae; non-protein amino acids +; sieve tube plastids also with fibres; leaves bicompound or not; (G adnate to side of hypanthium), ovules usu. campylotropous, outer integument with vascular strand; aril + (0), funicle long and thin to stout and thick, (pleurogram +); (seed with amyloid).

160[list]/1930: Senna (350), Chamaechrista (265). Predominantly tropical, esp. Africa and America. [Photos - Collection]

Synonymy: Caesalpiniaceae R. Brown, Cassiaceae Vest, Ceratoniaceae Link, Detariaceae Hess

3. Mimosoideae Candolle

Shrubs or trees (herbs); N-fixing common; albizziine [non-protein amino acid] +; sieve tube plastids also with fibres; (septate fibers +; aliform axial parenchyma); rays usu. 20³ cells high; leaves often bicompound, extrafloral nectaries common; flowers often aggregated into heads and developing together, bracteoles 0; flowers rather small, polysymmetrical, hypanthium often 0, K usu. connate, valvate (imbricate; much reduced), C usu. connate, valvate, odd member abaxial, claws 0; A often connate, polyads common, (G 1+ {Inga), stigma (dry - one record), cup-shaped, (peltate); (aril +), funicle long, thin, testa with vascular strand, pleurogram + (0), linea fissura common, U-shaped [open].

82[list]/3275: Acacia s. str. (960), Mimosa (480: some have sensitive leaves), Inga (350), Calliandra (200), Vachellia (161), Senegalia (85), Prosopis (45), Pithecellobium (40). Esp. tropical and warm temperate, esp. Africa and America (map: from Vester 1940; Maslin et al. 2003). [Photos - Collection]

Synonymy: Mimosaceae R. Brown

4. Faboideae Rudd, Papilionoideae Jussieu, nom. alt.

Herbs, vines (lianes, trees, shrubs); N-fixing common; isoflavonoids [pterocarpans and isoflavans], prenylated flavonoids, pyrrolizidine, indolizidine, and quinolizidine alkaloids +; (cork cambium deep seated); sieve tubes with spindle-shaped non-dispersive protein bodies; (nodes 1:1); leaves once compound, palmate or pinnate; K, C; A with unidirectional [abaxial to adaxial] initiation, ?hypanthium, adaxial-median C external [= ascending cochleate]; A usu. connate [e.g. 9 + 1]; (pollen porate); (G 1+ {Swartzia); ovules usu. campylotropous, (endothelium; integumentary endothelium); (aril +), pleurogram 0, linea fissura 0, hour-glass cells [below palisade exotesta] +, counter palisade + or 0, raphe shorter than the antiraphe, hilum with a hilar groove, tracheid bar [group of tracheids just below surface of hilum] +; embryo curved, with well-developed suspensor [?not the basal condition], radicle long, cotyledons accumbent, not investing radicle, cotyledon areole +, (endosperm 0; starch in embryo [inc. Swartzieae]).

476[list]/13855 (abbreviations - BAPH = baphioids, DAL = dalbergioids s.l., GEN = genistoids, IRLC = Inverted Repeat Loss Clade, MILL = Indigofereae + millettioids, MIRB = mirbelioids, ROB = robinioids, SWAR = swartzioids): Astragalus (2400-3270: IRLC), Indigofera (700: aff. MILL, mesifixed hairs), Crotalaria (700: GEN), Mirbelia s.l. (450: MIRB), Tephrosia (350: MILL), Desmodium (300: MILL), Aspalanthus (300: GEN), Oxytropis (300: IRLC), Adesmia (240: DAL), Trifolium (240: IRLC), Rhynchosia (230: MILL), Lupinus (200), Aeschynomene (160: DALB), Hedysarum (160: IRLC), Lathyrus (160: IRLC), Vicia (160: IRLC), Dalea (150: DALB), Eriosema (150: MILL), Lotononis (150: GEN), Millettia (150: MILL), Vigna (150: MILL), Swartzia (140: SWAR)), Daviesia (135: MIRB), Machaerium (130: DALB), Onobrychis (130: IRLC), Ormosia (130: unplaced), Lotus (inc. Coronilla: 125: ROB), Lonchocarpus (120: MILL), Erythrina (110: MILL), Gastrolobium s.l. (110: MIRB), Mucuna (105: MILL), Pultenaea (100: MIRB), Genista (90: GEN), Medicago (inc. Trigonella, 85: IRLC), Swainsonia (85: IRLC), Caragana (75: IRLC), Jacksonia (75: MIRB), Ononis (75: IRLC), Zornia (75: DALB), Argyrolobium (70: GEN), Arachis (70: DAL), Brogniartia (65: GEN), Cytisus (65: GEN), Bossiaea (60: MIRB), Canavalia (60: MILL), Clitoria (60: MILL), Dolichos (60: MILL), Galactia (60: MILL), Phaseolus (60: MILL), Sesbania (60: ROB), Derris (55: MILL), Lessertia (50: IRLC), Psoralea (50: MILL), Sophora (50: GEN), Caragana (50: IRLC). Esp. (warm) temperate, but world-wide (map: from Vester 1940; Meusel et al. 1965; Hultén 1971). [Photo - Flower, Fruit, Collection.]

Synonymy: Aspalanthaceae Martynov, Astragalaceae Martynov, Ciceraceae W. Steele, Coronillaceae Martynov, Galedupaceae Martynov, Hedysaraceae Oken, Inocarpaceae Zollinger, Lathyraceae Burnett, Lotaceae Oken, Papilionaceae Giseke, Phaseolaceae Postel, Robiniaceae Vest, Sophoraceae J. Weinmann, Swartziaceae Bartling, Tamarindaceae Berchtold & J. Presl, Viciaceae Berchtold & J. Presl

• Fabaceae may be recognised by their compound, stipulate leaves whose leaflets are entire and often have wrinkled pulvini, and flowers with a single carpel, free petals (or two may be connate), and stamens either all similar in length, or if dissimilar, not regularly alternating longer and shorter. The fruit is usually dry and elongated, the often flattened seeds being borne in a single rank.

• "Caesalpinioideae" and Cercis and its relatives are woody plants that may be recognised by their usually once-compound leaves and monosymmetric flowers with the odd petal adaxial and inside the others in bud; the hypanthium is often well-developed.

• Mimosoideae are also mostly woody plants that have leaves that are often bicompound and have extrafloral nectaries on the petioles. The flowers are rather small and are often borne in heads, all flowers opening more or less simultaneously; the long, coloured filaments form the visually attractive part of the inflorescence. Both the calyx and corolla are valvate, and both (and often the bases of the filaments) are connate. The seeds have a fine, U-shaped line on both sides.

• Faboideae are usually herbs or vines and often have once-compound leaves. The flowers are monosymmetric with the odd petal being adaxial and outside the others; the papilionoid flower consists of adaxial banner, paired wings and two connate petals forming the keel. The stamens have more or less connate filaments and the fruit is often explosively dehiscent, simultaneously splitting down both sides and the two valves twisting.

Evolution. Fabaceae are a notably speciose clade, particularly the branches with Mimosoideae and Faboideae (Magallón & Sanderson 2001), and contain ca 9.4% of eudicots; it has been estimated that some 16% of all woody species in neotropical rainforest are members of this family (Burnham & Johnson 2004). Indeed, Fabaceae are the most speciose family in lowland tropical rainforest and also drier forest types in America and Africa (Gentry 1988). They began diversifying in the Palaeocene only ca 60-64 million years ago (the stem group is little older), and the major clades had separated by 58-55 million years ago (e.g. Bruneau et al. 2008b; perhaps slightly younger in Bello et al. 2009). Bruneau et al. (2008b) suggest that the crown age of the major clades in Fabaceae is 56-34 million years ago. The clade [part of "Caesalpinioideae" + Mimosoideae] may date to 54 ± 3.4 million years before present, stem group Mimosoideae to ca 55 million years before present, crown group Mimosoideae to 44 ± 2.6 million years before present (Lavin et al. 2005). Wikström et al. (2001) provided somewhat different dates: they date the clade to 79-74 million years before present (Quillaja not included in the analysis), with diversification some 68-56 million years before present; the Mimosoideae-Faboideae split is dated to 59-34 million years before present. Stem group Faboideae may date to 58.6 ± 0.2 million years before present, and the crown group may be about the same age (Lavin et al. 2005, the latter date is rather sensitive to the age of Fabaceae as a whole). Although there are a number of transoceanic disjunctions within Fabaceae, 51/59 of these are only 1-22 million years old (Schrire et al. 2005).

Lavin et al. (2004) and Schrire et al. (2005) suggest that it is more profitable to think of diversification and distribution of Fabaceae in terms of vicariance of biomes rather than of the classic geographical areas; the North Atlantic land bridge may have been important in the Tertiary dispersal of the family (Lavin et al. 2000). Faboideae-Robinieae are an important component of the neotropical seasonally dry tropical forest where they have been diversifying for some 30 million years (Pennington et al. 2009). On the other hand, Inga (Mimosoideae), with some 350 species and an important component of neotropical lowland forests, seems to have diversified within the last two million years (Richardson et al. 2001b; Pennington et al. 2009 - extinction might also cause this pattern, see Crisp & Cook 2009). There has been much diversification of Indigofereae in succulent biomes, clades growing there tending to be geographically more restricted than those common in grassland biomes; ages of crown groups of the four clades into which species of the genus fall is ca 15.5 million years or less (Schrire et al. 2009). Crisp and Cook (2009) suggest that apparent independent increases in the rate of diversification in clades in the [Mirbelieae + Bossieae] and Podalyrieae are rather the results of extinctions caused by cooling climates and increased seasonality ca 32-30 million years ago in the early Oligocene, and Crisp and Cook (2007) date the development of SW/SE Australian disjunctions to vicariant events caused by the development of aridity in the Nullarbor plane some 14-13 million years ago (other climatic events could also be implicated).

Within Faboideae, a number of divergences have been dated, including the separation of the speciose Astragalus from Oxytropis 16-12 million years ago, although diversification in both is relatively recent; radiation in the speciose aneuploid New World neoastragalus species started ca 4.4 million years ago (Wojciechowski 2004). Lupinus has a recent (within the last two million years) Andean diversification of over eighty species, the rate of diversification icreasing as the genus moved into Andean South America from Central America (Moore & Donoghue 2009), and this was also probably associated with the migration of bumble bees, also from North America, at most six million years ago (Hughes & Eastwood 2006).

There are numerous often quite specific associations of insects and Fabaceae. Caterpillars of Lycaenidae-Riodininae-Riodinini, Lycaenidae-Curetinae and especially Lycaeninae-Lycaenini butterflies are often found on Fabaceae (Ehrlich & Raven 1964; Fiedler 1991, 1995), as are Pierid butterfly larvae (Coliadinae, Dismorphiinae: some 260 species in 15+ genera, about a quarter of the records - see also Brassicales and Santalales, Braby & Trueman 2006). The diversity of caterpillars - especially that of "basal" butterfly groups - on Fabaceae is such that Janz and Nylin (1998) and Braby and Trueman (2006) suggested that Fabaceae might be the springboard for hostplant diversification of butterflies feeding on angiosperms in general (see also the introduction to Fabales). In another variant of insect-plant relationships, the flowers of Crotalaria are visted by Danainae and Ctenuchidae because the pyrrolizidine alkaloids they contain are used as the basis of the pheromones of these lepidoptera (also Asteraceae, and wilting plants of some Boraginaceae: Edgar et al. 1974; Pliske 1975; Boppreé 1986); Crotalaria is also involved with arctiid moths such as Utetheisa in that its secondary metabolites provide defence for the young, pheromones, etc., etc. (Eisner & Meinwald 1995).

The jumping plant lice Psyllidae-Arytaininae are often associated with Fabaceae-Faboideae, especially genistoids, and especially in the Mediterranean-Macaronesian region, while Psyllidae-Acizzinae are associated with Mimosoideae in the Southern Hemisphere (Percy 2003; Percy et al. 2004). In Acacia s. str., well over 200 species of Phlaeothripinae (thrips) form galls and other habitations on species of subgenera Juliflorae and Plurinerves in Australia, although not on species of subgenus Acacia; the latter subgenus has only a single main vein, unlike the others which have several (Morris et al. 2002; Mound & Morris 2005). Much of the diversification sems to have occured subsequent to the radiation of of Acacia as aridification increased within the last 10 million years (McLeish et al. 2007). Bruchids (Chrysomeloidea-Bruchidae/Bruchinae), a large group with some 1700 species, have larvae that are specialized seed-eaters. They have diversified considerably on Fabaceae; perhaps first associated with Faboideae, they then moved on to other groups following the chemistry of the plants involved (esp. Kergoat et al. 2005a, b; see also Johnson 1989, 1990 [Acanthoscelides], Birch et al. 1989 [chemistry of the interaction], and Janzen 1969 [the complexity of the association between plant and weevil]). Two clades, made up largely of New World Acanthoscelides and predominantly Old World Bruchidius, dominate, and they may have radiated contemporaneously with their hosts, largely Fabaceae-Mimosoideae and Faboideae (elsewhere also on some Malvaceae, in particular); they can detoxify the non-protein amino acid, L-canavanine. The pattern of association of bruchid groups with mimosoids is interesting; individual bruchid genera tend to be found on adajcent pectinations of the mimosoid phylogenetic tree (Kergoat et al. 2007).

Finally, less widespread but very well known is the association of ants with some members of the old Acacia subgenus Acacia (= Vachellia). These includes the swollen-thorn acacias such as V. sphaerocephala which provide protein-rich Beltian bodies at the ends of the leaflets (the leaves have many leaflets, even for Acacia s.l.) as food for the Pseudomyrmex ants, and there are swollen stipular thorns that serve as their homes (Janzen 1974b, see Webber & McKey 2009 for comments on our understanding of this system). The ants also take nectar from extrafloral nectaries, and in the case of these close associations, the nectar produced is sucrose free, the ants lacking the invertase needed to break down sucrose (Kautz et al. 2009). Interestingly, species of Acacia with low rewards are derived from species with higher rewards and with ant mutualists that defend them; species that offer only low rewards are often colonized by exploiter ants that do not defend the plant (Heil et al. 2009). Examples of ant-plant relationship are scattered elsewhere in the family, and a recent study of the common African Leonardoxa africana details the importance of the third party in the relationships, an ascomycete (Defossez et al. 2009). Extrafloral nectaries are notably common in Mimosoideae, being found towards the base of the petiole and sometimes on petiolules, and the nectar usually has sucrose. Such nectaries are rare in "Caesalpinioideae", or they are represented by tufts of hairs (Pascal et al. 2000). However, they characterise a major clade within Senna, and there it has been suggested that they are a "key innovation" involved in plant defence and in the diversification of that clade, which is much more speciose than its sister taxon (Marazzi et al. 2006; Marazzi & Sanderson 2008).

Up to one third or more of the developing foliage of the species of Inga may be eaten by herbivores, and up to 43 species of this speciose genus may coexist at a single site. It has been suggested that this coexistence may in part be possible because species differ considerably in antiherbivore defences, the defences varying independently between the species (Kursar et al. 2009). Interestingly, the toxic indolizine alkaloid, swainsonine, in Oxytropis kansuensis at least is synthesised by the endophyte Undifilum (Pryor et al. 2009). Swainsonine is also found in the related Astragalus (species with it are called "locoweeds") and Swainsona, and it causes a serious, sometimes fatal, disease in cattle.

Indeed, the diversity of "secondary metabolites" in Fabaceae, perhaps especially in Faboideae, is remarkable; for instance, about 28% of all known flavonoids and about 95% of the isoflavonoid aglycone structures - over 1,000 alone - identified in plants are known from Fabaceae, and the isoflavonoids are restricted to Faboideae. Isoflavonoids may be phytoalexins (defence), and are perhaps also involved in nodulation (Hegnauer & Grayer-Barkmeijer 1993; Reynaud et al. 2004). In general Fabaceae have a very distinctive nitrogen metabolism. Non-protein amino acids are common (see e.g. Fowden et al. 1979), and nitrogen in the xylem sap is transported as a mixture of amino acids, amides, and sometimes also ureides; very little is transported as nitrate. Wojciechowski et al. (2003, 2004, see also Wojciechowski 2003) note that the evolution of some non-protein amino acids are systematically interesting, thus canavanine production seems to have originated in the ancestor of one major subgroup of Faboideae (it includes mirbelioids, millettioids, robinioids, and the large group lacking the inverted repeat in the chloroplast genome, and may date to 54.3 ± 0.6 million years before present - Lavin et al. 2005 - see tree above); canavanine and alkaloid production are mutually exclusive. Flavonoids lacking the 5-hydroxy group are characteristic of Fabaceae (Seigler 2003), but I do not know at what level they are apomorphic. Pea albumin, a small sulphur-rich peptide with insecticidal properties, is known only from Faboideae where it may be a synapomorphy for the [hologalegina + millettioid] clade, being lost in some/all robinioids (Louis et al. 2007). Finally, the presence of quinolizine and of pyrrolizidine alkaloids seems to be mutually exclusive within genistoid legumes (Wink 2008).

Fabaceae are well known for their association with nitrogen-fixing bacteria which grow inside irregular, pinkish-coloured nodules on the roots. Nodule formation is iniated by the exusation of flavonoids, isoflavonoids, and other attractants by the host and infection of a root hair by a bacterium, although there are other ways the plant becomes infected (Vessey et al. 2004). Although most nodulating bacteria are members of the proteobacteria α-2 subclass, they do not form a monophyletic group; Agrobacterium (crown gall tumour) and others are also members of this group (Sprent 2001). Rhizobium is perhaps the best-known genus involved. The plesiomorphic infection morphology shows persistent infection threads and long-lived nodules (see also Parasponia - Cannabaceae), while more derived may be the absence of infection threads, the mitosis of infected cells, and a short life span for the nodules (de Faria & Sprent 1995; see also Corby 1988 & Sprent 2005 for nodule distribution). Nodule formation involves the production of Nod factors by the bacterium. Remarkably, in a few nodule-forming α-proteobacteria such as the photosynthetic Bradyrhizobium there is no nodABC gene (Giraud et al. 2007). Nodulation is especially widespread in Faboideae and Mimosoideae, but less common in "Caesalpinioideae" - although occuring in taxa like Chamaecrista. It appears that the acquisition of the ability to nodulate has occured more than once, perhaps even several times, within the family. Within Faboideae, the nodulating Swartzia and immediate relatives may form a clade sister to the rest of the subfamily (support is weak, see Ireland et al. 2000; Pennington et al. 2000; Lavin et al. 2005), although some other Faboideae in clades that are also separate from that including the bulk of the subfamily do not nodulate. However, most Faboideae are nodulators (Sprent 2000, 2001, 2007). Generally speaking, symbiont specificity is greatest in the IRLC clade (Faboideae, see below), although genera like Astragalus are exceptions (Howard & Wojciechowski 2006). See Corby (1988) for a survey of nodules in Fabaceae and descriptions of the different morpologies involved; both the overall distribution of nodulation within Fabaceae and variation in nodule morphology are of some systematic significance (see e.g. J. J. Doyle 1994, 1998; J. J. Doyle et al. 1997; Lavin et al. 2001).

Evolution in nodulation in Fabaceae is still not well understood. Interestingly, a number of Fabaceae, perhaps especially non-nodulated members and including Acacia s. str. and "Caesalpinioideae" like Dicymbe, are ectomycorrhizal (Sprent & James 2007 for literature). Cluster roots have been reported in some Faboideae including Lupinus, although they do not occur in all members of the latter genus, at least (Shane & Lambers 2005). Finally, an variety of bacteria are being found to be associated with Fabaceae, including Burkholderia, a ß-proteobacterium not at all close to Rhizobium and relatives, which is also an effective nitrogen-fixing symbiont of at least some Faboideae and of Mimosa, and other ß-proteobacteria can form nodules, albeit ineffective, with Mimosoideae (Moulin et al. 2001; Sprent 2002; Elliott et al. 2007 and references); this kind of association may be quite common in the tropics (Sprent 2007).

Rusts show an interesting pattern of distribution on Fabaceae. Uromyces is found predominantly on herbaceous Faboideae, but also on Bauhinia and one or two other woody taxa (being found, along with related genera, on Acacia in Australia alone), while Ravenelia is found on woody members of the family, i.e. "Caesalpinioideae", but also especially Mimosoideae (Savile 1976, 1979a, b; El-Gazzar 1979). In a number of species of Ravenelia the teliospores, thick-walled spores in which nuclear fusion and then meiosis occur, are aggregated into groups, and these telial heads may mimic the groups of pollen grains (polyads) that are common in Mimosoideae. Stingless Trigona bees may pick up the telial heads and polyads as they forage for pollen. However, Ravenelia is only very rarely found on Australian Acacia; the distributions of rusts, acacias and trigonid bees all break at about Wallace's Line.

Although most Fabaceae have once or twice compound leaves, leaflets with entire margins, and pulvini associated with leaves and leaflets, there is extensive variation on this theme; palmate lewaves occur in Lupinus. In Acacia s. str. (the old subgenus Phyllodinae), the leaves of the mature plant are much modified and are often called phyllodes, but seedlings and regeneration shoots may have once or twice compound leaves. Kaplan (1980) suggested that these "phyllodes" were not equivalent to the petiole of a compound leaf, but to the leaf as a whole. In early development, instead of there being two, adaxial meristems that went on to develop the leaflets/pinnae, there was a single, broader adaxial meristem that developed to produce the entire leaf; these phyllodinous leaves are flattened at right angles to the plane of flattening of a normal leaf. In compound leaves, the leaflets/pinnae became lateral in position by secondary reorientation. In some species of Acacia phyllodinous leaves are densely set along the stem, but only some are associated with stipules and buds, others lacking both. A number of Faboideae (e.g. Vicia, Pisum) are tendrillar vines, the tendrils being modified terminal leaflets; in Lathyrus aphaca the photosynthetic function of the leaf is taken over by the large stipules, the rest of the leaf being tendrillar, while L. nissolia lacks tendrils and has a phyllodinous leaf. The leaves may be reduced to a single more or less connate pair of leaflets, as in Bauhinia, named after the botanical brothers Caspar and Jean Bauhin. Some species of Mimosa and other genera have leaves that are sensitive to touch, stimulus transmission occuring as membrane depolarisation is propagated down the petiole and along the stem; folding of the leaf is caused by tugor changes in the cells of the pulvini at the bases of the leaf and leaflets (for the anatomy of the pulvinus, which has an endodermis, see Rodrigues & Machado 2007). In taxa like Albizzia (Samanea) saman, similar movements occur as the leaflets fold towards the evening when the light is failing, or just when there is heavy cloud cover, this behaviour being responsible (in some tellings of the tale) for its name, the rain tree. In Desmodium gyrans the single pair of lateral leaflets move intermittently without being touched, the speed of movement increasing with the temperature. In general, leaf development is associated with the activity of the KNOX1 gene, as is common in plants with compound leaves, however, in the IRLC clade (Faboideae, see below) the KNOX1 gene is not expressed, the FLO/LFY gene, normally a floral regulatory gene, being expressed instead; the leaves have no pulvini (Champagne et al. 2007).

The "pea flower" or "papilionaceous" floral morphology (see below) and its variants are common in "Caesalpinioideae" and Faboideae. The flowers of Cercis are only superficially similar to those of Faboideae (Tucker 2002a), although both are more or less papilionoid and are similar functionally. The papilionoid flower is characterised by the more or less erect ultraviolet-absorbing banner petal which sometimes has colour patterning, the two wing petals, and the paired interlocking keel petals enclosing the stamens; bee pollination is the norm. Buzz pollination is quite common, and it occurs throughout the large genus Cassia ("Caesalpinioideae": Lewis et al. 2000) which has been divided into three. The flowers of Senna are often enantiostylous and lack bracteoles (enantiostyly is likely to have been acquired once, although also subsequently lost); the anthers are porose and basifixed. There are three stamen morphs: three adaxial staminodes, four middle medium-sized stamens from which pollen is taken by the bees, and three longer abaxial stamens pollen from which is actually involved in pollination (see Tucker 1996b; Marazzi & Endress 2008 for development). Cassia s. str., with dorsifixed anthers, also has three stamen morphs. The filaments are curved and the anthers have slits or basal pores. Finally, the largely herbaceous Chamaechrista is also enantiostylous; the stamens have two morphs in different whorls, the filaments are short, and the basifixed, porose anthers have a velcro-like line of hairs. Porose anthers in this whole clade have four different modes of development (Tucker 1996b). Bats may also be pollinators, as of Parkia (Mimosoideae). In Caesalpinia the abaxial sepal may be colorful and look like a keel, while in Hardenbergia violacea the colour patterning on the standard may mimic an anther (Lunau 2006). Papilionaceous flowers encompass a variety of morphologies; as Bruneau et al. (2005, p. 201) note of caesalpinioid legumes, "zygomorphy is expressed as a multitude of homoplasious morphs". Hardly surprisingly, flowers of Fabaceae attract a diversity of pollinators that visit the flowers for various rewards. Pollination in "Caesalpinioideae" is predominantly by polylectic bees, while oligolectic bees are commoner pollinators of Mimosoideae and Faboideae. However, this may be as much a reflection of where these subfamilies occur, since oligolectic bees are more speciose in (warm) temperate regions, especially Mediterranean climates (Michener 1979), and that is where the other two subfamilies are particularly common. Interestingly, within the tropics bees seem to be commonest in the New World tropics (Michener 1979), and woody Fabaceae are especially diverse there. Mirror image flowers are common in Fabaceae except for Mimosoideae (Tucker 1996b), while Hesse (1986) noted that both Bauhinia and Cercis - and Caesalpinia and Delonix - had pollen-connecting threads made up of something other than sporopollenin. Lewis et al. (2000: esp. "Caesalpinioidae") summarize pollination in Fabaceae.

Faboideae are pollinated in a variety of ways, their floral morphology varying accordingly (for a survey, see Arroyo 1981), although their pollen is relatively uniform (). When the androecium is monadelphous, i.e. the filaments of all the stamens are connate, the pollinator reward is often pollen, and this can be delivered by a pump secondary pollen presentation mechanism. The bee lands on the keel, and the style then forces pollen out of the keel in a tooth paste-like strand, as in Lupinus. If diadelphous - nine stamens are connate and a single adaxial stamen is free - the reward is often nectar, the nectary lying between the filament tube and gynoecium. Other taxa like Cytisus, Desmodieae and Indigofera have explosive pollination where the style is held under tension which is released as the style curves when the pollinator lands; such flowers can be visited only once. Vicia is another genus that has secondary pollen presentation: There the pollen is presented to the pollinator on a stigmatic brush. Erythrina is pollinated by both perching and hovering (humming) birds, and both floral morphology and how the flowers and inflorescences are held varies according the requirements of these different visitors (Bruneau 1997). Flowers of Swartzia (sister to all other Faboideae) are very distinctive with their single petal, numerous free and dimorphic stamens, and lack of nectar; pollination here may be by euglossine bees (see Torke & Schaal 2008 for a phylogeny).

Many Mimosoideae have very different floral morphologies from most other Fabaceae. Here numerous small and secondarily polysymmetric flowers are aggregated into attractive units, all flowers opening at about the same time. Pollen grains are frequently aggregated into polyads which are caught in the cup-shaped stigma that is of the appropriate size for the polyad of that species, and there are also about as many ovules as there are pollen grains in the polyad (Kenrick 2003 for references and the implications of this pollination mechanism for the breeding system). In Calliandra s. str. the polyads have an associated sticky mucilage body by which they are attached to the pollinator, but the stigma is much larger and capitate and the polyads adhere to its surface (Prenner & Teppner 2005; Greissl 2006, cf. in part Teppner 2007). For locellate anthers (scattered in the clade), polyads, anther dehiscence, etc., in Mimosoideae, see Prenner and Teppner 2005, Teppner (2007) and Teppner and Stabentheiner (2007) and references.

The legume s. str. is a single carpellate fruit that dehisces explosively along both sutures, the two valves twisting as they separate. The legume is common in European-North American Faboideae, but it occurs also in the other subfamilies, including in Bauhinia, the clade sister to the rest of the family. The fruits of Cercis, in the same clade, are not explosively dehiscent, but are otherwise similar; they are also typologically rather similar to the fruits of Myristica, the nutmeg! However, overall there is a great diversity of fruit morphology in the family, including variously winged fruits, fleshy fruits, fruits breaking up into single-seeded units in different ways, and fruits modified for animal transport with spines and hooks, for example, the velcro-like hooks on Desmodium (hence its common name, beggar's ticks). In Trifolium the calyx and corolla are both involved in fruit dispersal mechanisms. Arillate seeds are common, and seeds that have red and black color patterns such as Abrus, Erythrina and the sometimes pluricarpellate Pithecellobium are well known; these mimic the color contrasts of red aril and black seed of some other Fabaceae, and also other plants. There are also seeds with fleshy coats. However, in many taxa, especially those with explosively dehiscent fruits, the seed coat is very hard and may need scarification if germination is to occur (for fruits and seeds, see Corner 1951; van der Pijl 1956; Kirkbride et al. 2003; etc.). Close to a thousand Faboideae are myrmecochorous (Lengyel et al. 2009).

Knoblauch et al. (2001) discuss the possible mode of action of the distinctive spindle-shaped non-dispersive protein bodies (= forisomes), found commonly in Faboideae, in blocking the pores of the sieve plates when turgor pressure changes; the protein bodies change shape depending on the concentration of Ca²⁺ ions (Peters et al. 2007).

Cytisus purpureus forms a well-known graft hybrid with Laburnum anagyroides (+ Laburnocytisus adamii; see Herrmann 1951 for another example); the epidermis alone is Cytisus tissue, and any seeds, being derived from cells from deeper layers, will give Laburnum plants. However, the graft hybrid often breaks down, resulting in branches that are pure Laburnum anagyroides or pure Cytisus purpureus.

Economic Importance. For information on the domestication of soybean (Glycine max) common bean Phaseolus vulgaris, pea (Pisum sativum), the azuki bean (Vigna angularis) and relatives, see papers in Ann. Bot. 100(5). 2007, and for these taxa and lentil (Lens culinaris), see Fuller (2007). For the domestication of the peanut, Arachis hypogea, see Dillehay et al. (2007).

Chemistry, Morphology, etc. Root nodule morphology may help delimit groups of genera in Faboideae (Wojciechowski 2003). The ratio of galactose to mannose in the galactomannans (storage polysaccharides) in seeds of Fabaceae may be of phylogenetic interest (Buckeridge et al. 2000a, b). Some species of Mimosoideae and Faboideae have leaves that are rich in silica (Westbrook et al. 2009). Characters of woods of members of "Caesalpiniodeae" include rays that are usually more than 20 cells tall, presence of silica bodies, and axial canals (Evans et al. 2006); how these fit onto the tree is currently unclear.

Details of hypanthial evolution within Fabaceae are unclear; it seems to have become much reduced and lost several times. The "normal" (for flowering plants) floral orientation of Mimosoideae with the median sepal adaxial and the median petal abaxial may be secondary. Although the normal orientation is also found in some caesalpinioids like Ceratonia, the inverted orientation occurs in both Cercis and Bauhinia (see Tucker 1989; Herendeen et al. 2003; Luckow et al. 2005), many other caesalpinioids, and Faboideae.

For any understanding of floral development in Fabaceae, the numerous papers by Shirley Tucker are an essential starting point. The parts of the flowers of many Fabaceae develop in the unusual sequence sepals-carpels-petals-outer stamens-inner stamens, and there are other distinctive features of their development (e.g. Champagne et al. 2007; Feng et al. 2006; Wang et al. 2008); for variation in general patterns of floral development in Fabaceae, see Prenner and Klitgaard (2008b). Particularly when there is complete loss of floral structures in development, overall floral morphology can be greatly changed (Tucker 1988, 2000). In Bauhinia there are additional staminodial structures at the base of the ovary (Endress 2008c) - or perhaps they have something to do with colleters. For floral development in Mimosoideae, see Gemmeke (1982); the androecium may be centripetal when borne on five main primordia. Prenner (2004b) notes the distinctive cochlear-descending calyx aestivation, helically-initiated androecium, etc., of Calliandra s. str., rather isolated within Mimosoideae; for polyads, anther dehiscence, etc., see Teppner (2007) and Teppner and Stabentheiner (2007) and references. Pennington et al. (2000) discussed floral evolution in "basal" Papilionoideae, some of which like Swartzia have flowers with very derived morphologies. Polysymmetry in the African Cadia (Faboideae-genistoid), a "reversal", is the result of dorsalization of the flower (the same basic principle as peloria in Antirrhinum: Citerne et al. 2006); Cadia is sister to the largely Cape group of genera of the Podalyrieae-genistoids (Boatwright et al. 2008a). For floral and inflorescence morphology, especially in Faboideae-Loteae, see Sokoloff et al. (2007a). The pattern of initiation of the sepals and stamens in Faboideae is variable, by no means always being unidirectional (e.g. Prenner 2004a; de Chiara Moço & de Araujo Mariath 2009 - cf. characterization). The flowers of some Amorpheae have a stemonozone rather than a hypanthium (McMahon & Hufford 2002). Prenner (2004c) suggested that a slight asymmetry in the early development of the androecium (the adaxial median stamen is initiated slightly off the median axis) occurs in more "basal" Faboideae and also some "Caesalpinioideae". Androecial initiation in Swartzia can be both centripetal and centfugal.

Caesalpinioideae have 4(-7)-nucleate tapetal cells, while those of Mimosoideae and Faboideae are 1-nucleate (Wunderlich 1954) - this character may have some systematic significance. Pollen variation in Fabaceae is quite considerable outside Faboideae (Bente Klitgaard, pers. comm.), that of Duparquetia being unique among that of angiosperms (Banks et al. 2006). The style is at least sometimes hollow, although the cavity arises in various ways, including by lysigeny (Lersten 2004). The carpels may have five traces and are quite often open during development in "Caesalpinioideae", but not, apparently, in Cercideae, Mimosoideae or Faboideae (Tucker & Kantz 2001). The embryo sac of some Faboideae (?elsewhere) more or less protrudes into the micropyle, as in Archevaletaia (Maheshwari 1950). There is a great deal of variation in the development of the embryo suspensor, even within Faboideae (Lersten 1983; see also Tucker 1987; Yeung & Meinke 1993; Rodriguez-Pontes 2008). Both a true endothelium and an integumentary endothelium may be present in Faboideae (Rodrigues-Pontes 2008 for discussion and references). For seed and embryo morphology in Faboideae, see Kirkbride et al. (2003). For the aborting plumule in seedlings of Lotus and Coronilla and their relatives, see Dormer (1945).

Luckow et al. (2005) discuss variation in flower and seed in the Mimosoideae; for information on seed anatomy, see Gunn (1981) and on fruits and seeds in "Caesalpinoideae", see Gunn (1991), for anatomy, see Gasson et al. (2003). For general information see Polhill and Raven (1981), Ferguson and Tucker (1994), Crisp and Doyle (1995), Doyle and Luckow (2003), and Lewis et al. (2005: well-illustrated summary of geographic distribution, etc., of all the genera; some of the taxa recognised in the body of the book are para/polyphyletic). For general chemistry, about which a great deal is known, see Hegnauer (1994, 1996), Southon (1994), and Hegnauer and Hegnauer (2001), and for additional details, see also Frohne and Jensen (1992) and Waterman (1994: secondary metabolites), for the evolution of these secondary metabolites, see Wink and Waterman (1999), Wink and Mohamed (2003: particularly useful) and Wink (2003), for polysaccharides and flavonoids in particular, see Hegnauer and Grayer-Barkmeijer (1993) and Harborne and Baxter (1999), for terpenoids, see Langenheim (1981, 2003), for seed galactomannans, see Buckeridge et al. (2000b), for alkaloids, see Aniszewski (2007), and for glucosylceramides, see Minamioka and Imai (2009). For wood anatomy, see Baretta-Kuipers (1981), Gasson et al. 2009 ("Caesalpinioideae"-Caesalpinieae), and Evans et al. (2006: Mimosoideae), starch, Czaja (1978), embryology, etc., Dnyansagar (1970), general floral and inflorescence morphology, Endress (1994b), epidermal wax crystals, Ditsch et al. (1995), gene and intron loss, J. J. Doyle et al. (1995), floral development, Tucker (1996a, b and references, 2001 [Cynometreae], 2003) and Mansano and Teixeira (2008), pollen morphology, Banks and Klitgaard (2000), Banks et al. (2000), and Kuriakose (2007), cotyledon areoles, Endo and Ohashi (1998), and for the pleurogram, esp. in Chamaechrista, De-Paula and Oliveira (2008).

Phylogeny. Fabaceae are monophyletic in both molecular and morphological analyses, although the family is sometimes dismembered into three (e.g. Takhtajan 1997). Relationships at the base of Fabaceae are currently unresolved. In addition to placing Cercideae, etc., as sister to the rest of Fabaceae, Wojciechowski et al. (2004) found Dialeae were sister to the remainder. There were then two main clades, the Mimosoideae, to which Ceratonia, Gleditsia, etc., Caesalpinieae, Cassieae, and Cercideae (all "Caesalpinioideae") are more or less successively sister taxa, and Faboideae; Bruneau et al. (2008a, b) found a somewhat similar set of relationships (see tree here). Cercis and Bauhinia may be sister to all other Fabaceae (e.g. J. J. Doyle et al. 2000 and references; Bruneau et al. 2001), although they are placed sister to Detarieae s.l. (inc. Cynometra) sometimes with only with moderate support (Wojciechowski et al. 2004; Lavin et al. 2005; Forest et al. 2007b). Detarieae include genera like Cynometra, Tamarindus and Amherstia and have also been placed by themselves as sister to all Fabaceae minus Cercideae. Duparquetia is also in this general area (Forest et al. 2002; Tucker et al. 2002). Recent studies (Bruneau et al. 2008a, b) find that Detarieae s.l., Duparquetia, and/or Cercideae are all candidates for being sister to the rest of the family. Morphology and anatomy support such relationships. Thus all three lack vestured pits (they are also absent in Cassieae), but such pits are common in the rest of the family, i.e. their presence is largely congruent with phylogeny. Generic limits of Bauhinia itself are discussed by Sinou et al. (2007), and at least Bauhinia lacks the srp12 intron (Doyle et al. 1995; Lai et al. 1997). The standard of Duparquetia shows colour patterning. The parts of the flower show normal acropetal initiation, unlike the case in many other legumes (Prenner & Klitgaard 2008a, esp. b for details of floral development). Detarieae are well known for showing extensive loss of petals and/or stamens, or increase in the latter (Tucker 1992b, 2000, etc.); thus in Monopetalanthus durandii the flower is surrounded by bracetoles and the floral formula is K 1 (minute), C 1; A 10; G 1, Brachystegia glaucescens also has large bracteoles, K 5 (all small), C 0; A 10; G 1, while Dialium guineense has small bracteoles, and a floral formula of K 5, C 1 (small); A 2; G 1 (Tucker 2000). Many Detarieae have crater-like glands on the abaxial surfaces of the leaflets, they secrete resin, having secretory canals in the stem, they have caducuous stipules and bracteoles, etc. (Redden & Herendeen 2006; morphological phylogenetic analysis; Fougère-Danezan et al. 2003, 2007: molecular study, characters of the group). The resins produced by Detarieae contain distinctive bicylic diterpenes, possibly an apomorphy for the tribe (Fougère-Danezan et al. 2007). Pollen is also extremely variable in this group (Banks & Klitgaard 2000). Detarieae s. str. and Amherstieae have amyloid in their cotyledons, x = 12 (Hegnauer & Grayer-Barkmeijer 1993); amyloid is also found in Sclerolobieae (?different classifications?: see Kooiman 1960). Finally, in a classic study Léonard (1957) described seedlings of some African members (Cynometreae, Amherstieae) of this group.

Whatever the relationships among these three clades, the rest of Fabaceae form a clade. Mimosoideae in the old sense are very largely monophyletic, as are Faboideae, but their recognition makes Caesalpinioideae paraphyletic. Umtiza is excluded from Detarieae and forms a clade with taxa like Gleditsia, Gymnocladus and Ceratonia, several of which are dioecious and have smallish, greenish flowers sometimes with a poorly differentiated calyx and corolla - not plesiomorphic features (Herendeen et al. 2003a; see also Forest et al. 2007b). For additional information on relationships in caesalpinioid legumes, see Herendeen et al. (2003b) and Lavin et al. (2005), and for phylogenetic relationships within Senna, see Marazzi et al. (2006), for some pollen morphology, see Banks et al. (2003).

Some ex-caesalpinioids (e.g. Dimorphandra), which have small flowers in spikes or panicles, may have to be included in Mimosoideae (Wojciechowski 2003; Bruneau et al. 2008a, b), to which they show considerable similarity in wood anatomy (Evans et al. 2006) and also pollen, rather homogeneous although nearly always in monads (Banks & Lewis 2009), and/or Mimosoideae would have to be reduced to a tribe (Luckow et al. 2003). Ingeae are embedded in Acacieae or vice versa (e.g. Clarke et al. 2000; Robinson & Harris 2000; Miller & Bayer 2000, 2001; Luckow et al. 2003; Jobson & Luckow 2007; Brown 2008; Brown et al. 2008). The old Acacia subgenus Acacia, which includes the bull's horn acacias, seems to be monophyletic, but Acacia s.l. is polyphyletic. As Maslin (2001) noted sadly of the 955 or so species then placed in Acacia for the Flora of Australia treatment, "we are obliged to present the flora treatment [i.e., everything in the one genus] in the absence of a more meaningful classification". However, maybe things will change (Maslin et al. 2003) - the argument now is over what names to call the bits into which Acacia s.l. is to be divided (see above). Murphy et al. (2000, 2003) and Miller et al. (2003) discuss the phylogeny of Acacia s. str., the old subgenus Acacia Phyllodinae, and Miller and Bayer (2003) that of Vachellia, the old subgenus Acacia, and Senegalia, the old subgenus Aculeiferum. Siegler (2003) summarized the phytochemistry of the complex, Evans et al. (2006) detailed wood anatomy, and Kergoat et al. (2007) noted what bruchids had to say about systematics of Acacia s.l.; see also Muelleria 26(1). 2008, a special issue on Acacia, and also World Wide Wattle website. Of other Mimosoideae, Mimosa may be monophyletic and sister Piptadenia (Besseger et al. 2008). See Pennington (1997) for a monograph of Inga, Richardson et al. (2001b) for its diversification. Catalano et al. (2008) provide a phylogeny of the ecologically important New World genus Prosopis.

Faboideae are monophyletic. A topology (simplified) for Faboideae in general including [swartzioids: SWAR [Cladrastis, etc., [genistoids: GEN, [Amorpheae + dalbergioids = dalbergioids s.l.: DAL], [baphioids: BAPH [mirbelioids: MIRB [[Indigofereae + millettioids: MILL] [robinioids: ROB + Inverted Repeat Loss Clade: IRLC]]]]]]] seems moderately well supported (Wojciechowski 2003; McMahon & Sanderson 2006). Note that the [robinioids + Inverted Repeat Loss Clade] clade is the hologalegina clade. Within Faboideae, Swartzieae, woody, nodulators, lacking bracteoles, with very variable flowers and arillate seeds, may be sister to the rest, but support is weak and the exact circumscription of Swartzieae is unclear (Ireland et al. 2000; Pennington et al. 2000; Lavin et al. 2005); it may well be largely restricted to Swartzia. Swartzia has atypical seeds for Faboideae, for example, the testa being thin and cracking and the embryo straight, but these are likely to be derived features. Florally it is also distinctive: it has an entire calyx that is cast off as the flower opens, only a single petal, numerous free and dimorphic stamens, a stalked ovary, and no nectary; some taxa have more than one carpel (see Torke & Schaal 2008 for a phylogeny).

For information about testal anatomy of Faboideae, see Kirkbride and Wiersema (1997) and Lackey (2009); many features other than those noted in the characterisation above may be of interest, including the presence of two recurrent vascular bundles lateral to the hilum, absent in "basal" Faboideae (Lackey 2009). Many Faboideae have a 50kb inversion in the trnL intron in the large single-copy region of their chloroplast genome, however, taxa like Swartzieae, Sophora, and a few others, lack this inversion (J. J. Doyle et al. 1996, 1997; Pennington et al. 2001; Wojciechowski et al. 2004). There has also been the loss of the 25kb chloroplast inverted repeat; this characterises a largely temperate, epulvinate, herbaceous and very speciose group, although Wisteria is also a member of this clade, the IRLC group (see Wojciechowski 2003 and references). Desmodium and possibly related genera (MILL) have also lost the rps12 intron (it has moved to the nucleus) as well as the srp12 intron (Doyle et al. 1995; Bailey et al. 1997; Jansen et al. 2008). ORF84 has also been lost many times, and accD (= ORF512, zpfA) has also been lost (Doyle et al. 1995). Both the rps16 and ycf4 genes are lost in the majority of tribes of Faboideae (Doyle et al. 1995; Jansen et al. 2007). Overall, these and other changes in chromosomal organisation provide a considerable amount of phylogenetic structure. McMahon and Sanderson (2006) provide a supermatrix analysis of 2228 Faboideae.

The IRLC clade is characterized not only by the loss of the inverted repeat, but the compound leaves lack pulvini and the KNOX1 gene is not expressed early in development, although the (normally floral) FLO/LFY gene is (Champagne et al. 2007). All members of the IRLC clade lack the clpP intron, while the rps12 intron has been lost from all members of the clade examined except Wisteria, Callerya and Afgekia - but not Glycyrrhiza - cf. the tree above (Jansen et al. 2008; Wojciechowski et al. 2008; see also Saski et al. 2007). Within the IRLC, Astragalus is an extremely speciose genus characterising drier areas of both hemispheres, and a number of taxa have leaf rhachis spines. Extensive phylogenetic studies (e.g. Wojciechowski 1993, 2004; Kasempour Osaloo et al. 2004; Scherson et al. 2004) show most New World taxa are aneuploid (n = 11-15) and form a monophyletic group, other species are base 8. Oxytropis is sister to Astragalus. For a phylogeny of Caragana, see Zhang et al. (2009). Within Trifolium the American species form a monophyletic group (Ellison et al. 2006; Liston et al. 2006). Phylogenetic relationships within Medicago have turned out to be highly reticulating (Maureira-Butler et al. 2008); Medicago probably includes Trigonella, and for its limits, see Bena (2001).

For the phylogeny of dalbergioid legumes, see Lavin et al. (2000); desmodioid nodules, small oblate nodles of determinate growth that are always associated with a lateral root, are common there (Lavin et al. 2001). For relationships within Amorpheae and the floral evolution of the latter (petals may be lost, or all look rather similar; a stemonozone, a tube formed by the adnation of filaments to the corolla, may be developed; etc.), see McMahon and Hufford (2002, 2004, 2005) and McMahon (2005), for that of Robinia and its relatives, which include Lotus and Sesbania, which are quite close, see Lavin et al. (2003) and Farruggia and Wojciechowski (2009), of Crotalarieae, see Boatwright et al. (2008c), and for that of Psoraleae, see Egan and Crandall (2008). For diversification in Cape genistoids, see Edwards and Hawkins (2007), and for phylogenies or revisions of Mirbelia s.l., see Crisp and Cook (2003a, b), Pultenaea, Orthia et al. (2005), Jacksonia, Chappill et al. (2007), Ononis, Liston (1995), Arachis, Krapovickas and Gregory (2007 - for the domestication of the peanut, see Dillehay et al. 2007), Cytisus, Cubas et al. (2002), on Bossiaea (60: MIRB). Members of the millettioid clade have a pseudoracemose inflorescence with more than a single flower at each node (Tucker 1987a; Indigofereae, its sister clade, have true racemes (Wojciechowski et al. 2004). Hu et al. (2000) studied the phylogeny of Millettieae, Kajita et al. (2001: rbcL) that of Millettieae and relatives. Stefanovic et al. (2009: eight chloroplast genes) concetrated on relationships among the some 2,000 species of Millettieae-phaseoloids, finding substantial resolution; i.a. Mucuna was sister to Desmodium and its relatives, the combined clade being sister to the rest of the group, which includes Cajanus, Vigna, Erythrina etc. For a phylogeny of Phaseolus itself, see Delgado-Salinas et al. (2006). Schrire et al. (2009) disentangle relationships within Indigofereae, finding considerable phylogenetic structure (i.a. there are four major clades within Indigofera) that can be linked with both morphology and ecology.

Classification. For a sectional classification of the neotropical Swartzia (Faboideae), see Torke and Mansano (2009).

Previous Relationships. Fabaceae s.l. are often referred to their own order, as in both Cronquist (1981) and Takhtajan (1997). They can be confused with Connaraceae (Oxalidales), although the latter lack stipules, their flowers are polysymmetrical and have stamens of two distinctly different lengths, and their gynoecium is frequently multicarpellate. However, in both the RP122 chloroplast gene has moved to the nucleus, and the ovaries of both have adaxial furrows (cf. the ventral slit: Matthews & Endress 2002). Fabaceae have also been linked with Sapindaceae (e.g. Dickison 1981b), here in the malvids, but there is little support other than the common possession of compound leaves - and none molecular - for such an association.

Surianaceae + Polygalaceae: ?

SURIANACEAE Arnott, nom. cons.   Back to Fabales

Woody; ellagic acid?; cork also in inner cortex; storying +/0; wood fluorescing?; (sieve tube plastids with starch grains and protein filaments forming a peripheral shell); nodes 3:3 (1:1 - Suriana); sclereids +; petiole bundle arcuate to annular; leaves spiral or two-ranked (pinnate, leaflets alternate, articulated), (stipules 0 - Suriana); inflorescence cymose, usu. terminal, pedicels articulated; K connate basally or not, quincuncial, C (0), contorted, shortly clawed or not, staminodial tissue ± foriming a ring round the C base; A (= and opposite sepals) 10, obdiplostemonous, (gynophore and disc - Recchia); G 1-5, when 5 opposite petals, 1-5 unitegmic campylotropous ovules/carpel, ovules surrounded by mucilage, hypostase +, styles ± gynobasic, stigma clavate to capitate; fruit a berry, drupe or nut, endocarp with outer layer of palisade sclereids, other cells apart from the inner epidermis isodiametric, K persistent, accrescent or not; exotestal cells enlarged, cuboidal, tanniniferous, rest crushed [ca 7 cells thick]; chalazal endosperm haustorium +, embryo curved or folded, cotyledons incumbent; n = ?; germination epigeal, phanerocotylar.

5[list]/8 Mostly Australian, also Mexico (Recchia), pantropical (Suriana maritima) (map: from van Steenis & van Balgooy 1966 [blue - Suriana maritima]). [Photo - Flower]

Chemistry, Morphology, etc. The vegetatively "atypical" Suriana is the only genus whose embryology has been studied and the whole family is little known chemically. The family is vegetatively very heterogeneous, although quite homogeneous in wood anatomy (Webber 1936). The exotesta of Suriana is described as being green (Rao 1970).

For more information, see Jadin (1901) and Boas (1913: both vegetative anatomy), Gutzwiller (1961: general), Rao (1970: embryology, etc., under Simaroubaceae), Hegnauer (1973, as Simaroubaceae: chemistry), Gadek and Quinn (1992: pericarp), Ito and Tobe (1994: embryology), Crayn et al. (1995: relationships), Schneider (2006: general), and floral development (Bello et al. 2007/8: Suriana only). Additional data from: Cadellia - Benson s.n. = NSW 408528 (anatomy); Stylobasium - Latz 12864 (fruit), Strid 20708 (anatomy).

Phylogeny. For relationships, see Forest et al. (2007b); [[Recchia + Lundellia] [Suriana [Cadellia + Stylobasium]] seems to be the cladistic structure in the family. Although the sieve tube plastids of Stylobasium are distinctive, having sieve starch grains and protein filaments forming a peripheral shell (Behnke et al. 1996), there seems little reason to recognise Stylobasiaceae as a monotypic family since three more would be needed

Previous Relationships. Surianaceae were included in Rosales-Simaroubaceae (here in Sapindales) by Cronquist (1981) and in Rutales as a separate family by Takhtajan (1997).

Synonymy: Stylobasiaceae J. Agardh

POLYGALACEAE Hoffmannsegg & Link, nom. cons.   Back to Fabales

Successive cambia +); saponin +; nodes 1:1; styloids 0; (stomata other than anomocytic); plant glabrous or with unicellular hairs; branching from previous flush; often paired glands [crateriform extrafloral nectaries] or thorns at nodes (elsewhere); inflorescence indeterminate; flowers monosymmetric, K quincuncial, caducous, C 5, A (2-)8(-10), median adaxial A often absent, pollen polycolporate, surface psilate or foveolate, (disc excentric); G connate, micropyle zigzag (exostome often long; exostomal), nucellar cap +, style long, stigma dry; fruit a berry; seed often hairy, (exostomal/funicular aril +), exotesta subsclerotic, endotestal cells ± palisade or not, U-thickened, crystalliferous (not); hypostase enlarges; endosperm copious or not, starchy.

Ca 21[list]/940 - four tribes below. World-wide, except the Arctic and New Zealand. [Photo - Flower]

1. Xanthophylleae Chodat

Shrubs or trees; plants Al accumulators; wood parenchyma apotracheal, diffuse; glands at nodes, (conspicuous domatia on leaves), K quincuncial, unequal; A (7-)8(-10); G [2], placentation parietal, 2 or more apotropous ovules/carpel, in two rows, outer integument 4-12 cells across, stigma small, bilobed (capitate); (fruit irregularly dehiscent); testa multiplicative; hypostase massive; n = ?

1/95. Indo-Malesia (map: from van der Meijden 1982).

Although the seed coat anatomy is often undistinguished, some species have Polygala-type testa anatomy (see family characterisation); irregularly loculicidally dehiscent fruits also occur.

For a monograph, see van der Meijden (1982).

Synonymy: Xanthophyllaceae Reveal & Hoogland

The Rest: A ± adnate to petals, variously connate, often monadelphous, anthers opening by short apical slits, 1 epitropous ovule/carpel.

2. Polygaleae Chodat

Herbs (echlorophyllous mycoheterotrophs), lianes, shrubs; (ergoline alkaloids +), at least some smell of wintergreen, tannins 0 [Polygala]; pits vestured; banded paratracheal parenchyma +; (glands at nodes); two adaxial lateral K = wings, 2 abaxial lateral K, minute, two connate adaxial C = the standard, abaxial C = the keel, often fringed, 2 abaxial-lateral C minute, (A 2-)8; G [2] (adaxial member suppressed), stylar canal +, stigma bilobed, ± asymmetrical; fruit an often flattened capsule, drupe or samara, (K persistent, green - Polygala, etc.); caruncle + (chalazal aril +; no appendages)n = 6+, very variable.

Ca 13/830: Polygala (325, generic limits unclear), Monnina (180), Muraltia (120), Securidaca (80). World-wide, except the Arctic and New Zealand (Map: from GBIF 2009; FloraBase 2009; orange from Paiva 1998).

3. Carpolobieae Eriksen

(glands at nodes); abaxial C keeled; A (4) 5; G [3], stigma capitate; n = 9-11.

2/6. Tropical Africa.

4. Moutabeae Chodat

Woody; plants Al accumulators; banded apotracheal parenchyma +; glands on leaves (and at nodes); abaxial C not keeled; A (6-)8-10; G [3-8], stigma capitate; funicular aril +; n = 14.

4/15. Tropical America, New Guinea to New Caledonia. [Photos - Flowers, Flower - Close-up, Petioles, Branch, Petioles with ants, Flower with moth]

For vegetative anatomy, see Styer (1977).

Synonymy: Diclidantheraceae J. Agardh, Moutabeaceae Endlicher

• Polygalaceae are woody or herbaceous plants that may be recognised by their often yellowish-drying simple and entire leaves; there are quite frequently paired glands at the nodes or glands or domatia on the leaf blades. The flowers are usually monosymmetric, and are more or less papilionaceous. They range from having five rather large sepals and five petals - not strongly papilionaceous - to having two of the sepals much enlarged and coloured (the "wings" of the flower), two of the petals much reduced, and the three remaining petals modified as "standard" and "keel" - strongly papilionaceous. There are two or more carpels and a single style.

Evolution. Wikström et al. (2001) date the origin of the clade to 68-66 million years before present (ca 84 million years in Bello et al. 2009 - but note topology), with diversification beginning in the Tertiary (65.5-)57.4(-49.3) million years ago (Bello et al. 2009). In the Cape region Muraltia started diverifying in the Fynbos (21.4-)18.5(-14.1) million years ago, and in the succulent karoo (4-)2.5(-1.3) million years ago (Verboom et al. 2009). The distinctive Paleosecuridaca curtisii has recently been described from the Palaeocene of North Dakota; although in gross morphology its fruits are remarkably like those of Securidaca and the seeds have a testa with a well developed palisade layer, there are two seeds per carpel (Pigg et al. 2008b).

In a study of ant dispersal in Polygalaceae, which is quite common in Polygaleae, it seems that caruncles may be an apomorphy of Polygaleae, although chalazal arils have also evolved more than once in this clade, and they and caruncles have been lost, too (Forest et al. 2007b; see also Lengyel et al. 2009). Evolution of these elaiosomes is suggested to have occured (69.9-)54-50.5(-35.2) million years before present, well after initial diversification of the ant clades attracted to them. Muraltia, with some 120 species found mostly in the Cape region, appears to have diversified relatively recently, mostly within 10 million years (Forest et al. 2007a).

Epirixanthes is an echlorophyllous mycoheterotroph. In at least some North American species of Polygala pollen is presented on the sterile lobes of the asymmetrical stigma (secondary pollen presentation: Weekley & Brothers 1996; see Castro et al. 2008 for details).

Although genera like Xanthophyllum and some Moutabeae may have paired glands at the nodes, other genera seem to lack anything faintly comparable with stipules, and where stipules might be lost in this part of the tree is uncertain.

The flower in Polygalaceae is quite differently constructed from that of Fabaceae (but see Prenner 2004d), although quite often both looking and being functionally very similar. However, the flowers of Polygala, which in overall appearance are particularly like those of some Fabaceae, are unlikely to represent the plesiomorphic condition of the family, indeed, overall floral variation in Polygalaceae is very considerable. In Polygala myrtifolia, with eight stamens, it is apparently the two stamens in the median plane - i.e., on opposite sides of the flower - that are lost (Prenner 2004d). For floral morphology and development of Polygaleae, see Krüger and Robbertse (1988) and Krüger et al. (1988). The tricolpate pollen of Balgooya is probably derived; some Polygalaceae such as Heterosamara have asymmetric, almost boat-shaped pollen grains (Banks et al. 2008).

Some general information is taken from Eriksen (1993a) and especially from Eriksen and Persson (2006), that on ovule and seed from Verkeke (1985, inc. integument thickness, the inner integument of Securidaca is up to 9 cells across, 1991), Takhtajan (2000: ovule and seed), and Banks et al. (2008: pollen morphology and evolution). For chemistry, see Hegnauer (1969, 1990). Also see Polygalaceae website (Freire-Fierro 2001 onwards).

Phylogeny. Of the four groups mentioned above, Moutabeae may be paraphyletic (Persson 2001: trnL-F), although adding rbcL data suggests they are monophyletic (Forest, in Eriksen & Persson 2006), and morphology points in this direction (Eriksen 1993b); the other three groups appear to be monophyletic (although Carpolobieae are only weakly supported). However, all four tribes are strongly supported in a three-gene analysis (Forest et al. 2007b), and Xanthophylleae are sister to the other three tribes; relationships between the latter are unclear. Polygala and Bredemeyera are grossly paraphyletic (Persson 2001). See Eriksen (1993b) for a morphological phylogeny.

Classification. See Paiva (1998) for much information on Polygala, especially from Africa and Madagascar.

Previous Relationships. The Polygalales of Cronquist (1981) included seven families, the mutual affinities of five of which were described as being "widely accapted". These include Xanthophyllaceae (= Polygalaceae), Vochysiaceae (Myrtales), Trigoniaceae (Malpighiales) and Tremandraceae (= Elaeocarpaceae, Oxalidales). For Emblingiaceae, often included in (e.g. Cronquist 1981; Mabberley 1997) or near (e.g. Takhtajan 1997) Polygalaceae, see Brassicales.