Hedysarum L.

Scientific Description

Family Papilionaceae. Hedysareae.

Habit and leaf form. Herbs; not resinous. Biennial, or perennial; plants with neither basal nor terminal concentrations of leaves; to 0.4–1 m high. Mesophytic. Leaves small, or medium-sized; alternate; distichous; ‘herbaceous’; not imbricate; petiolate; non-sheathing; gland-dotted, or not gland-dotted; aromatic, or without marked odour; compound; epulvinate; pinnate; imparipinnate. Leaflets 7, or 11, or 15. Lateral leaflets opposite. Leaflets not stipellate; pulvinate, or epulvinate; flat, or folded. Leaf blades dorsiventral. Leaves with stipules. Stipules intrapetiolar; adnate to the petiole, or free of the petiole; free of one another; scaly (scarious); caducous, or persistent. Leaf blade margins entire. Leaves without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes (spicate), or in heads. The terminal inflorescence unit cymose, or racemose. Inflorescences axillary; pedunculate, crowded racemes, the peduncle longer than the axillant leaf. Flowers pedicellate, or subsessile; bracteate (the bracts scarious or setaceous); bracteolate (the bracteoles beneath the calyx, setaceous); small to medium-sized; fragrant; very irregular; zygomorphic. The floral asymmetry involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending, with the posterior petal outside and forming the ‘standard’); basically 5 merous. Floral receptacle developing a gynophore, or with neither androphore nor gynophore. Free hypanthium present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous; five lobed; imbricate, or valvate; campanulate; regular to unequal but not bilabiate (the lobes subequal); persistent; non-accrescent; with the median member anterior. Corolla present; 5; 1 -whorled; appendiculate, or not appendiculate. Standard not appendaged. Corolla partially gamopetalous. 2 of the petals joined (the two ventral petals connivent to form the ‘keel’). The joined petals anterior. The wings of the corolla free from the keel; not laterally spurred. Standard ‘normally’ developed; not sericeous. Keel conspicuously exceeding the wings; not long-acuminate/beaked (blunt); neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); deep red (in H. coronarium); deciduous. Petals clawed. Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; all equal, or markedly unequal; coherent (the joined filaments constituting a staminal tube for much of their length, their free parts upturned); 2 - adelphous (9+1, the tenth, posterior stamen free of the rest at least above and below); 1 -whorled (although diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape; diplostemonous; both opposite and alternating with the corolla members. Anthers separate from one another, or connivent; all alike; dorsifixed (the connective broad); versatile; dehiscing via pores, or dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. 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 abruptly (in-) bent (above the anthers). Style filiform. Style glabrous. Stigmatic tissue terminal. Carpel 4–50 ovuled. Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile, or subsessile. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy; not spinose (muricate). The fruiting carpel indehiscent; a loment (the segments nearly orbicular). Pods much elongated; not triangular; not becoming inflated; more or less flat, or somewhat compressed; regularly constricted between adjacent seeds; transversely septate between the seeds; wingless. Dispersal unit the loment segment. Fruit 4–50 seeded. Seeds reniform; endospermic, or non-endospermic; not mucous; compressed; small, or medium sized; non-arillate. Cotyledons 2; accumbent. Embryo curved, or bent. Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar.

Physiology, biochemistry. Nitrogen-fixing root nodules present. Aluminium accumulation not found. Photosynthetic pathway: C₃.

Geography, cytology, number of species. World distribution: Europe, Mediterranean, Asia, North America. Adventive. 2n=14, 16 (48). A genus of about 100 species; 1 species in Western Australia; H. coronarium L.

Additional comments. Description based mainly on H. coronarium.