Lotus L.

Scientific Description

Family Papilionaceae. Loteae.

Habit and leaf form. (Sub-) shrubs, or herbs (softly hairy); not resinous. Annual, or biennial, or perennial; plants with neither basal nor terminal concentrations of leaves. Helophytic, or mesophytic. Leaves small to medium-sized; alternate; spiral, or distichous; ‘herbaceous’; not imbricate; petiolate to sessile; non-sheathing; compound; epulvinate; pinnate; imparipinnate. Leaflets usually 5 (the proximal pair stipule-like, the other three crowded towards the tip of the rachis); pulvinate, or epulvinate; flat, or folded. Leaf blades dorsiventral. Leaves with stipules (minutely), or without stipules. Stipules intrapetiolar; adnate to the petiole; free of one another; scaly, or represented by glands; 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; via hymenoptera (commonly by bees).

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually), or solitary; not crowded at the stem bases; when solitary, axillary; in cymes, or in heads, or in umbels, or in fascicles. Inflorescences simple. The terminal inflorescence unit cymose. Inflorescences axillary (pedunculate); pedunculate, few-flowered ‘cymose heads’ or ‘umbels’. Flowers pedicellate; bracteate. Bracts persistent (bracts 1–3, leaflike). Flowers ebracteolate; small; very irregular; zygomorphic; not resupinate. 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 with neither androphore nor gynophore. Free hypanthium present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; (five) lobed. Calyx lobes about the same length as the tube to markedly longer than the tube. Calyx imbricate, or valvate; regular, or unequal but not bilabiate, or bilabiate; non-fleshy; persistent; non-accrescent. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate, or not appendiculate (the wings at least sometimes auriculate). Standard not appendaged (but the claw with infolded margins). 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; laterally spurred, or not laterally spurred. Standard ‘normally’ developed; not sericeous. Keel conspicuously exceeded by the wings to conspicuously exceeding the wings (incurved); long-acuminate and beaked, or not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); yellow (commonly), or white, or red, or pink, or purple; deciduous; non-accrescent. Petals clawed. Fertile stamens present. Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; markedly unequal (the filaments alternately long and short); coherent (with the filaments united basally into a tube); 2 - adelphous (the posterior, vexillary member sometimes free of the rest); 1 -whorled (even though diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; distinctly dissimilar in shape (the alternate, longer filaments dilated distally); diplostemonous; both opposite and alternating with the corolla members. Filaments alternately filiform and club-shaped. Anthers separate from one another, or connivent; all alike; dorsifixed; versatile; dehiscing via pores, or dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains. Fertile gynoecium present. 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 (above the ovary, then straight). Style glabrous. Stigmatic tissue terminal, or oblique. Carpel 7–50 ovuled (‘many’). Placentation marginal (along the ventral suture). Gynoecium median. Ovary sessile. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit sessile; non-fleshy; not hairy; not spinose (smooth). The fruiting carpel dehiscent; a legume. Pods much elongated (linear); not triangular; straight to curved (no more than slightly curved); not becoming inflated; somewhat compressed, or terete; transversely septate between the seeds, or not transversely septate; wingless. Valves of the dehisced pod twisted. Fruit 1 celled. Dispersal unit the seed. Fruit 7–25 seeded (‘many’?). Seeds endospermic; not mucous; compressed to not compressed (globular to lenticular); small; non-arillate. Cotyledons 2; accumbent. Embryo chlorophyllous; curved, or bent (the radicle inflexed). Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar (the plumule sometimes suppressed, with shoots developing from the axils of the cotyledons).

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

Geography, cytology, number of species. Native of Australia and adventive. 2n= (10), 12, 14, 24, 28. A genus of about 100 species; 5 species in Western Australia (2 native).