Zornia J.F.Gmel.

Scientific Description

Family Papilionaceae. Aeschynomeneae.

Habit and leaf form. Herbs. Perennial; plants with neither basal nor terminal concentrations of leaves; to 0.2–2 m high. Mesophytic, or xerophytic. Leaves small to large; alternate; spiral; ‘herbaceous’, or leathery; not imbricate; subsessile. Petioles wingless. Leaves non-sheathing; gland-dotted; compound; pulvinate; bifoliolate, or palmate. Leaflets 2, or 4; not stipellate; pulvinate, or epulvinate; flat, or folded; without lateral lobes. Leaf blades dorsiventral. Leaves with stipules. Stipules intrapetiolar. Stipules more or less peltate. Stipules free of one another; persistent. Leaf blade margins entire. Leaves without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening 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. The terminal inflorescence unit racemose (the flowers solitary in the bract axils). Inflorescences terminal, or axillary, or leaf-opposed; in ours, few-flowered racemes. Flowers pedicellate; bracteate (the bracts almost reduced to their stipules, hence ‘paired, stipule-like’); (bi-) bracteolate; small; 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 with neither androphore nor gynophore. Free hypanthium present (short), or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; (five) lobed; imbricate, or valvate; bilabiate (upper lip 2-lobed, lower 3-lobed with the central lobe longer than the laterals); persistent; non-accrescent; with the median member anterior. Corolla present; 5; 1 -whorled; appendiculate (the wings auriculate), or not appendiculate. Standard not appendaged. Corolla polypetalous (the keel petals often more or less free), or partially gamopetalous. When partially gamopetalous, 2 of the petals joined (the two ventral petals connivent to form the ‘keel’). The joined petals of the papilionate corolla anterior. The wings of the corolla free from the keel; not laterally spurred. Standard ‘normally’ developed; entire, or emarginate; not sericeous. Keel conspicuously exceeded by the wings to conspicuously exceeding the wings; long-acuminate and beaked to not long-acuminate/beaked (‘subrostrate’, incurved); neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); white, or yellow, or orange; deciduous. Petals clawed, or sessile. 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; 1 - adelphous (the tube closed, persistent after the upper parts of the filaments are shed). The staminal tube free from the keel petals. Androecial members 1 -whorled. 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; dimorphic; dorsifixed; versatile; dehiscing via pores, or 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 filiform. Style glabrous. Stigmatic tissue terminal. Carpel (2–)4–9 ovuled. Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit aerial; sessile; non-fleshy; hairy to not hairy; not spinose. The fruiting carpel indehiscent; a loment (with (1-)2–6 segments). Pods much elongated; not triangular; more or less straight; not becoming inflated; somewhat compressed (the segments globular or cuboid); regularly constricted between adjacent seeds (the upper margin straight, the lower lobed); transversely septate between the seeds; wingless. Loment segments rounded or cuboid. Fruit 1 celled; elastically dehiscent, or passively dehiscent; (1–)2–6 seeded. Seeds reniform (asymmetric); endospermic, or non-endospermic; not mucous; compressed; small; non-arillate. Cotyledons 2; accumbent. Embryo curved, or bent. Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar, or cryptocotylar.

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

Geography, cytology, number of species. Native of Australia. 2n=20. A genus of about 86 species; 6 species in Western Australia.