Rhynchosia Lour.

Scientific Description

Family Papilionaceae. Phaseoleae.

Sometimes included in Leguminosae.

Habit and leaf form. (Sub) shrubs, or lianas, or herbs, or herbaceous climbers; evergreen, or deciduous; resinous, or not resinous. Perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Self supporting (or prostrate), or climbing; the climbers stem twiners. The twiners twining anticlockwise. Mesophytic, or xerophytic. Leaves small to medium-sized; not fasciculate; alternate; spiral, or distichous; not decurrent on the stems; ‘herbaceous’, or leathery; not imbricate; petiolate. Petioles wingless. Leaves non-sheathing; not gland-dotted (but with conspicuous sessile glands); compound; pulvinate; ternate (with asymmetric basal leaflets). Leaves pinnately trifoliolate. Leaves imparipinnate. Leaflets 3; 1–5.5 cm long. Lateral leaflets opposite. Leaflets stipellate (stipels setaceous). Leaflets without swollen, glandlike stipels. Leaflets pulvinate; rhombic, or ovate, or obovate, or orbicular; cuneate at the base, or rounded at the base; flat; with conspicuous lateral lobes, or without lateral lobes. Leaflet margins flat. Leaf blades dorsiventral; cross-venulate. Leaves with stipules. Stipules intrapetiolar. Stipules not peltate. Stipules free of the petiole; free of one another; scaly, or leafy; persistent. Leaf blade margins entire; not prickly; flat. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs present; complex hairs absent. Branched hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring, or anomalous.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the disk. Pollination mechanism conspicuously specialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually), or solitary; not crowded at the stem bases; in racemes, or in panicles. Inflorescences simple, or compound. The terminal inflorescence unit cymose, or racemose. Inflorescences terminal, or axillary; axillary or terminal racemes or panicles. Flowers pedicellate; bracteate. Bracts deciduous. Flowers ebracteolate; small to medium-sized; very irregular; zygomorphic. The floral asymmetry involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending); basically 5 merous; tetracyclic. Floral receptacle developing a gynophore to with neither androphore nor gynophore. Free hypanthium present, or absent. Hypogynous disk present; intrastaminal. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed; toothed (the lobes acuminate). Calyx lobes about the same length as the tube, or markedly longer than the tube. Calyx imbricate; exceeded by the corolla; bilabiate (the two lobes of the upper lip more or less joined); neither appendaged nor spurred; non-fleshy; persistent; non-accrescent; with the median member anterior. Corolla present; 5; 1 -whorled; appendiculate (the standard auriculate). Standard appendaged (auriculate). Corolla partially gamopetalous. 2 of the petals joined, or 4 of the petals joined. The joined petals anterior. The wings of the corolla adherent to the keel, or free from the keel; not laterally spurred. Standard ‘normally’ developed; entire, or emarginate; not sericeous (but with abaxial hairs and glands). Keel not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); hairy abaxially (and glandular); plain, or with contrasting markings (e.g. sometimes striped); yellow, or yellow and red, or yellow and brown; deciduous; non-accrescent. Petals clawed. Androecial members definite in number. Androecium 10. Androecial members free of the perianth; all equal, or markedly unequal; coherent; 2 - adelphous (9+1). The staminal tube free from the keel petals. Androecial members 1 -whorled. Androecium exclusively of fertile stamens. Stamens 10; diplostemonous; both opposite and alternating with the corolla members; filantherous. Anthers separate from one another to connivent; all alike; dorsifixed; versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains. Gynoecium 1 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic. Style (in-) curved (above). Style hairy but not bearded, or glabrous. Stigmatic tissue terminal. Carpel 2 ovuled. Placentation marginal. Gynoecium median. Ovary sessile to subsessile. Ovules funicled; pendulous to ascending; biseriate; minutely arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit aerial; about 16–24 mm long; non-fleshy; hairy (and glandular). The fruiting carpel dehiscent; a legume. Pods much elongated; not triangular; curved (falcate); not becoming inflated; more or less flat, or somewhat compressed; regularly constricted between adjacent seeds, or not constricted between the seeds; not transversely septate; wingless; not internally hairy. Valves of the dehisced pod not twisted. Fruit 1 celled; elastically dehiscent. Dispersal unit the seed. Fruit (1–)2 seeded (longitudinal in the pod). Seeds non-endospermic; not mucous; compressed (subreniform); small; non-arillate (and the funicle attached in the middle of the hilum, which is parallel with the axis of the fruit); not conspicuously hairy; wingless. Cotyledons 2; accumbent. Embryo curved to bent. Testa hard; non-operculate; smooth; homogeneous in colour, or conspicuously colour-patterned (often mottled). Micropyle zigzag, or not zigzag. Seedling. Germination cryptocotylar.

Special features. Calyx limb 5 lobed (the upper pair more or less joined). Upper lip of calyx lobed; 2 lobed. Lower lip of calyx lobed; 3 lobed.

Geography, cytology, number of species. Native of Australia. 2n=22; ploidy levels recorded 2. A genus of about 200 species; 4 species in Western Australia.