Eriosema (DC.) G.Don
Gen.Hist. 2:347 (1832)

Name Status: Current
Browse to the list of specimens for Eriosema (DC.) G.Don

Scientific Description
Leslie Watson, Thursday 8 September 2016

Family Papilionaceae. Phaseoleae.

Sometimes included in Leguminosae.

Habit and leaf form. Erect herbs; evergreen, or deciduous; resinous (with yellow deposits on the undersides of leaves, and on calyx and corolla). Plants unarmed. Perennial (with annual aerial stems). Leaves cauline. Plants with neither basal nor terminal concentrations of leaves; to about 0.25–0.8 m high; tuberous. Self supporting. Mesophytic. Leaves small to medium-sized (20–72 mm long); not fasciculate; alternate; spiral, or distichous; not decurrent on the stems; ‘herbaceous’, or leathery; not imbricate; shortly petiolate (or rather, petiolulate); non-sheathing; not gland-dotted (but with sessile, orange glands); aromatic, or without marked odour; compound (commonly), or simple (ostensibly); pulvinate, or epulvinate; unifoliolate. Leaflets 1; 2–7.2 cm long; not stipellate. Leaflets without swollen, glandlike stipels. Leaflets pulvinate, or epulvinate; narrowly ovate; cordate, or rounded at the base; flat; without lateral lobes. Leaflet margins revolute. Leaf blades dorsiventral; cross-venulate. Mature leaf blades adaxially with sparse long and short hairs; abaxially with dense short hairs, some long hairs, and sessile glands. Leaves with stipules. Stipules intrapetiolar. Stipules not peltate. Stipules free of the petiole; free of one another; scaly (scarious); persistent (striate, attenuate). Leaf blade margins entire; not prickly; flat. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs present (sessile, orange). Unicellular hairs absent. 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’; not crowded at the stem bases. Inflorescence few-flowered. Flowers in racemes. The terminal inflorescence unit racemose. Inflorescences axillary; short axillary racemes. 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. Calyx lobes markedly shorter than the tube to markedly longer than the tube. Calyx imbricate; exceeded by the corolla; slightly bilabiate; neither appendaged nor spurred; non-fleshy; persistent; non-accrescent; with the median member anterior. Calyx lobes triangular. 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 to emarginate; not sericeous (but with sparse hairs and glands). Keel about equalling the wings (about 8 mm); not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); hairy abaxially (and glandular); yellow; deciduous; non-accrescent. Petals clawed. Androecial members definite in number. Androecium 10. Androecial sequence not determinable. Androecial members free of the perianth; markedly unequal (the posterior member short); coherent; 2 - adelphous (1+9). The staminal tube adnate to the keel petals, or 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 bent (at or below the middle). Style glabrous. Stigmatic tissue terminal. Carpel 2 ovuled. Placentation marginal. Gynoecium median. Ovary sessile to subsessile. Ovary summit hairy, the hairs not confined to radiating bands. Stigmas very small. Ovules funicled; pendulous to ascending; biseriate; arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit aerial; 10–13 mm long; sessile; non-fleshy; densely hairy (with ferruginous hairs); not spinose. The fruiting carpel dehiscent; a legume. Pods somewhat elongated to much elongated; not triangular; straight; not becoming inflated; somewhat compressed (hairy); 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 2 seeded. Seeds non-endospermic; not mucous; not compressed (ovoid to obloid); small (4–5 mm long); arillate (the prominent aril rimlike). Cotyledons 2; accumbent. Embryo curved, or bent. Testa hard; non-operculate; smooth; conspicuously colour-patterned (mottled). Micropyle zigzag, or not zigzag. Seedling. Germination cryptocotylar.

Special features. Calyx limb 5 lobed. Upper lip of calyx lobed; 2 lobed (the lobes partly connate). 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 130 species; 1 species in Western Australia.

Taxonomic Literature

  • Wheeler, J. R.; Rye, B. L.; Koch, B. L.; Wilson, A. J. G.; Western Australian Herbarium (1992). Flora of the Kimberley region. Western Australian Herbarium. Como, W.A.