The Families of Angiosperms

L. Watson and M.J. Dallwitz

Leguminosae Adanson

Alternatively Fabaceae Lindl. (but ambiguous).

Including Caesalpiniaceae R.Br., Cassiaceae Link, Ceratoniaceae Link, , Detariaceae (DC.) Hess, Hedysareae (Hedysaraceae) J.G Agardh, Lathyraceae Burnett, Lotaceae Burnett, Mimosaceae R. Br., Papilionaceae Giseke, Phaseolaceae Ponce de Léon & Alvares, Robiniaceas (Robiniaceae) Welw., Swartzieae (Swartziaceae (DC.) Bartl.

Habit and leaf form. Trees, or shrubs, or herbs, or lianas; resinous, or not resinous. ‘Normal’ plants, or switch-plants; the switch forms often with the principal photosynthesizing function transferred to stems, or phyllodineous. Leaves well developed (usually), or much reduced (not infrequently). The herbs annual, or biennial, or perennial; without conspicuous aggregations of leaves. Self supporting, or epiphytic, or climbing; the climbers stem twiners, or tendril climbers (via stem or leaf tendrils), or scrambling (then sometimes via hooks); the twiners twining clockwise, or twining anticlockwise (in Phaseolus, Wisteria). Helophytic, or mesophytic, or xerophytic. Conspicuously heterophyllous (e.g. Acacias with bipinnate juvenile and phyllodineous mature foliage), or not conspicuously heterophyllous. Leaves persistent, or deciduous; minute to very large; alternate (usually), or opposite to whorled (e.g. some Mirbelieae); spiral, or distichous; ‘herbaceous’, or leathery, or membranous, or modified into spines; petiolate to sessile; non-sheathing; gland-dotted, or not gland-dotted; aromatic, or without marked odour (usually); with blades borne edgewise to the stem (commonly when phyllodineous, especially in Australia), or with blades ‘normally orientated’; compound (commonly), or simple; pulvinate, or epulvinate; when compound (as is usual) unifoliolate, or ternate, or pinnate (commonly,), or palmate, or bipinnate (commonly), or bifoliolate (or the single organ deeply to shallowly bilobed, or apically retuse - e.g., Bauhinieae); when pinnate, imparipinnate, or paripinnate. Leaflets pulvinate, or epulvinate. Leaves stipulate (nearly always), or exstipulate (e.g., some Mirbelieae). Stipules intrapetiolar; scaly, or leafy, or spiny, or represented by glands; caducous, or persistent. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Leaves with ‘pearl glands’ (rarely), or without ‘pearl glands’. Mucilaginous epidermis present, or absent. Stomata anomocytic, or paracytic, or anisocytic, or tetracytic, or cyclocytic. Hairs of numerous kinds present (in the family). Urticating hairs absent (but present on calyces and pods of Mucuna). Lamina with secretory cavities, or without secretory cavities. Secretory cavities containing oil, or containing mucilage, or containing resin. The mesophyll containing mucilage cells, or not containing mucilage cells; with sclerenchymatous idioblasts (occasionally), or without sclerenchymatous idioblasts. Minor leaf veins with phloem transfer cells (55 genera, including some from each subfamily), or without phloem transfer cells (67 genera. Watson and Gunning (1981) detail Caesalpinioideae and Papilionoideae. For Mimosoideae, Pate and Gunning (1969) recorded as positive species of Mimosa, Neptunia and (dubiously) Calliandra; they recorded negatives for Acacia, Albizzia, Adenenanthera, Dichrostachys, Enterolobium, Leucaena, Pithecellobium, Prosopis and Wallaceodendron).

Axial (stem, wood) anatomy. Secretory cavities present, or absent. Cork cambium present (usually), or absent; initially deep-seated, or initially superficial. Nodes tri-lacunar, or penta-lacunar. Primary vascular tissues in a cylinder, without separate bundles, or comprising a ring of bundles. Internal phloem absent. Cortical bundles present, or absent. Medullary bundles absent. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous. The anomalous secondary thickening when present, via concentric cambia (e.g. Koompassia, Derris, Mucuna, Wisteria).

The vessel end-walls simple. The vessels with vestured pits, or without vestured pits. The axial xylem at least sometimes including septate fibres, or without septate fibres. The parenchyma apotracheal, or paratracheal. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones, or not stratified. ‘Included’ phloem present, or absent. The wood storied, or partially storied (VPI).

Reproductive type, pollination. Unisexual flowers present, or absent. Plants hermaphrodite (mostly, in Caesalpinioideae and Papilionoideae), or monoecious, or andromonoecious, or polygamomonoecious (unisexual flowers commoner in Mimosoideae). Pollination entomophilous, or ornithophilous (especially common in southern Australia), or chiropterophilous (e.g. Mucuna holtoni, where the nectar guide is a petal functioning as a ‘concave mirror’ for ultrasound); mechanism conspicuously specialized (with at least two forms of passive presenter, involving modifications of the style and/or of the keel of the corolla and/or the staminal filaments, and explosive pollination in (e.g.) Medicago), or unspecialized.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary; when aggregated, in panicles, or in fascicles, or in racemes, or in spikes, or in heads. The ultimate inflorescence units cymose, or racemose (— often ostensibly racemose, but frequently paniculate or, as in many Phaseoleae, having pseudoracemes bearing nodal clusters of obscure constitution). Inflorescences terminal, or axillary, or leaf-opposed (e.g. in some Bossiaeeae); pseudanthial (e.g. Mimosoideae), or not pseudanthial. Flowers minute to large; regular (Mimosoideae), or somewhat irregular to very irregular (Papilionoideae, most Caesalpinioideae); commonly zygomorphic; resupinate (sometimes, in association with bird pollination or in pendulous inflorescences), or not resupinate. The floral irregularity involving the perianth and involving the androecium. Flowers papilionaceous (Papilionoideae), or ‘pseudo-papilionaceous’ (‘ascending’ in most Caesalpinioideae), or neither papilionaceous nor pseudo-papilionaceous (regular in Mimosoideae); tetracyclic (mostly), or pentacyclic to polycyclic. Floral receptacle developing a gynophore (this often adnate to the hypanthium in Caesalpinioideae), or with neither androphore nor gynophore; usually more or less cupular. Free hypanthium present, or absent (more or less replaced by the calyx tube in most Papilionoideae). Hypogynous disk present, or absent.

Perianth with distinct calyx and corolla (nearly always), or sepaline (corolla at least sometimes absent in 26 genera of Caesalpinioideae, some Swartzieae, some Amorphieae); (3–)5, or (6–)10(–11); 1 whorled (rarely), or 2 whorled; isomerous, or anisomerous. Calyx 5, or (3–)5(–6); 1 whorled; polysepalous, or partially gamosepalous, or gamosepalous (characteristic of most Mimosoideae and Papilionoideae). In Caesalpinioideae, sometimes 2 of the members joined. Calyx unequal but not bilabiate, or bilabiate, or regular; persistent (usually), or not persistent (e.g., Lamprolobium); accrescent (rarely), or non-accrescent; imbricate, or valvate (or splitting irregularly in the Swartzieae); when pentamerous, with the median member anterior. Epicalyx present (e.g., Pultenaea), or absent (usually). Corolla (1–)3–5 (commonly reduced below five or missing in Swartzieae, Amorphieae and Caesalpinioideae, commonly 3–4 in Mimosoideae); 1 whorled; appendiculate (petals variously auriculate, lobed, etc.), or not appendiculate; polypetalous (commonly in Caesalpinioideae), or partially gamopetalous (usually, in Papilionoideae), or gamopetalous (in some Mimosoideae and Sympetalandra). Papilionoideae commonly with 2 of the petals joined (the two ventral petals connivent to form the corolla ‘keel’), or 4 of the petals joined (the wings adnate to the keel). The joined petals of the papilionate corolla anterior (or anterior and lateral). Corolla imbricate (descending in Papilionoideae, ascending in Caesalpinioideae), or valvate (Mimosoideae), or with open aestivation (occasionally); white, or yellow, or orange, or red, or pink, or purple, or blue; or some members persistent (e.g. Trifolium), or deciduous. Petals clawed, or sessile.

Androecium (1–)9–10, or 10–50 (often 9–10, but commonly fewer, especially in Caesalpinioideae, and sometimes ‘many’ in Mimosoideae, Swartzieae, Sophoreae). Androecial members free of the perianth (mostly), or adnate (e.g. in Caesalpinioideae-Parkieae, Dalbergieae, Mirbelieae, Trifolium, Genista, etc., where at least some members or the androecial tube can be attached to corolla components); all equal, or markedly unequal; free of one another (sometimes), or coherent (in a variety of configurations); when cohering 1 adelphous, or 2 adelphous (commonly with the tenth, posterior stamen free of the rest, whose filaments are united into a tube); 1 whorled (when five, nine or ten, though the antesepalous, theoretically ‘outer’ members develop first, are often longer, and their anthers may differ from those of the antepetalous members), or 2–6 whorled (? in some Mimosoideae). Androecium exclusively of fertile stamens (usually, and nearly always in Papilionoideae), or including staminodes. Stamens (1–)9–10(–50); reduced in number relative to the adjacent perianth, or isomerous with the perianth, or diplostemonous to polystemonous. Anthers separate from one another, or connivent; dorsifixed, or basifixed, or dorsifixed and basifixed (alternating); versatile (commonly), or non-versatile; dehiscing via pores, or dehiscing via longitudinal slits; introrse, or latrorse; bilocular (usually), or unilocular to bilocular (the thecae sometimes confluent above); tetrasporangiate; appendaged, or unappendaged. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Anther wall initially with one middle layer, or initially with more than one middle layer; of the ‘dicot’ type. Tapetum usually glandular. Pollen shed in aggregates (often in Mimosoideae, infrequently elsewhere, e.g. Afzelia), or shed as single grains (usually); when aggregated, in tetrads, or in polyads. Pollen grains aperturate (usually), or nonaperturate; (2–)3(–4) aperturate, or 6 aperturate; colporate (commonly), or porate (the pores sometimes operculate), or colpate, or rugate; 2-celled (nearly always), or 3-celled (rarely, in Mimosoideae).

Gynoecium 1 carpelled (nearly always), or 2–16 carpelled (in a few Mimosoideae from New Guinea and tropical Australia (Archidendron) and tropical South America (Affonsea, Klugiodendron); partly petaloid (Petalostylis), or non-petaloid. Carpels reduced in number relative to the perianth (nearly always), or isomerous with the perianth to increased in number relative to the perianth (rarely). The pistil 1 celled (nearly always), or 2 celled (by a false septum, e.g. Mirbelia). Gynoecium monomerous (usually), or apocarpous; of one carpel (usually), or eu-apocarpous (rarely); superior. Carpel apically stigmatic; (1–)2–100 ovuled (i.e. to ‘many’, usually in alternating rows along the placenta). Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile to stipitate. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral (Papilionoideae, Mimosoideae), or persistent (most Caesalpinioideae). Synergids hooked (often with filiform apparatus). Endosperm formation nuclear. Endosperm haustoria present; chalazal, or lateral (rarely). Embryogeny onagrad, or asterad, or caryophyllad.

Fruit non-fleshy, or fleshy. The fruiting carpel dehiscent, or indehiscent; a legume (usually), or a follicle, or an achene, or samaroid, or a loment, or drupaceous. Fruit elastically dehiscent, or passively dehiscent. Gynoecia of adjoining flowers combining to form a multiple fruit (rarely, in Mimosoideae), or not forming a multiple fruit. Dispersal unit the seed, or the fruit. Fruit (1–)2–100 seeded (to ‘many’). Seeds endospermic, or non-endospermic (endosperm copious only in some Caesalpinioideae); small to very large; winged (e.g. in some Mimosoideae), or wingless (usually). Seeds with starch, or without starch. Seeds with amyloid, or without amyloid. Cotyledons 2; usually flat. Embryo chlorophyllous (45/83 — representing all three subfamilies); straight, or curved, or bent (the radicle straight in Mimosoideae, straight or oblique in Caesalpinioideae, usually inflexed in Papilionoideae). The radicle when flexed, lateral. Micropyle zigzag, or not zigzag.

Seedling. Germination phanerocotylar, or cryptocotylar. Nitrogen-fixing root nodules present (seemingly the norm in Papilionoideae and Mimosoideae), or absent (seemingly, from many Caesalpinioideae).

Physiology, phytochemistry. C₃. C₃ physiology recorded directly in Acacia, Alysicarpus, Amorpha, Arachis, Astragalus, Caragana, Cassia, Cercidium, Crotalaria, Dalea, Dolichos, Genista, Gleditsea, Glycine, Hoffmanseggia, Indigofera, Lespedeza, Lotus, Lupinus, Medicago, Mimosa, Olneya, Phaseolus, Pisum, Prosopis, Pueraria, Robinia, Sesbania, Spartium, Stylosanthes, Tephrosia, Trifolium, Vicia, Vigna. Anatomy non-C₄ type (recorded from numerous genera representing all three sybfamilies). Sugars transported as sucrose (in numerous species and genera from all three subfamilies). Cyanogenic (rarely), or not cyanogenic (mostly). Cynogenic constituents tyrosine-derived, or phenylalanine-derived, or of Hegnauer’s ‘Group C’, or leucine-derived. Alkaloids present (commonly), or absent. Arbutin present, or absent. Iridoids not detected. Proanthocyanidins present, or absent; when present, cyanidin, or delphinidin, or cyanidin and delphinidin. Flavonols present (mostly), or absent; kaempferol and quercetin, or quercetin and myricetin, or kaempferol, quercetin, and myricetin. Ellagic acid consistently absent (from 54 species and 41 genera, representing all three subfamilies). Aluminium accumulation not found. Sieve-tube plastids P-type (mostly), or S-type (in a few Papilionoideae only); when P-type type IV (subtype (a) in Mimosoideae, (b) elsewhere).

Geography, cytology. Holarctic, Paleotropical, Neotropical, Cape, Australian, and Antarctic. Frigid zone, temperate, sub-tropical, and tropical. Cosmopolitan.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Fabiflorae; Fabales. Cronquist’s Subclass Rosidae; Fabales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Fabales.

Species 12000. Genera about 650; Mimosoideae: Albizia, Inga, Pithecellobium, Acacia, Mimosa, Prosopis, Piptadenia, Entada, Parkia, etc. Caesalpinioideae: Caesalpinia, Parkinsonia, Delonix, Gleditsea, Haematoxylum, Sclerolobium, Melanoxylon, Bauhinia, Cercis, Cassia, Ceratonia, Colophospermum, Copaifera, Brachystegia, Tamarindus, Amherstia, etc. Papilionoideae: Sophora, Baphia, Podalyria, Glycine, Phaseolus, Vigna, Crotalaria, Lupinus, Cytisus, Medicago, Trifolium, Lotus, Indigofera, Astragalus, Vicia, Lathyrus, Pisum, Arachis, Aeschynomene, etc.

General remarks. Clearly, the many features which tend distinguish the subfamilies all involve rather numerous exceptions, are very incompletely documented, or are not universally applicable.

Economic uses, etc. Economically very important for food, fodder, fibres, dyes, gums, resins, oils, and ‘green manure’; e.g. peas (Pisum), lentils (Lens), peanuts (Arachis), beans (Phaseolus, Vicia), cowpeas (Vigna), soybean (Glycine), clover (Trifolium), alfalfa (lucerne, Medicago), lupins (Lupinus), sweet clover (Melilotus). Numerous cultivated ornamentals, e.g. Bauhinia, Wisteria, Acacia, Cassia, Cytissus, Genista, Albizia, Lathyrus. Important tropical timbers from Acacia, Albizzia, Dalbergia, Robinia, Sophora, etc.

Quotations.

This fellow pecks up wit as pigeons peas
(‘Love’s Labour’s Lost’, v., 2)

. . . . luscious as locusts
(‘Othello’, i., 3 - Ceratonia)

Like a richly coloured map
Square platts of clover red and white
Scented wi’ summer’s warm delight
(John Clare c. 1820, ‘A Sunday with Shepherds and Herdboys’)

For Linnaeus
Knelt before it on the sod,
For its beauty thanking God
(Of Ulex europaeus. Quoted by Ann Pratt, ‘Wild Flowers’ (1857), unattributed. Seems to derive from Sir J.E. Smith’s (fairy?)tale of Linnaeus’s reaction on seeing flowering furze on Putney Common)

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2024. delta-intkey.com’.

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