Erodium Aiton

Scientific Description

Family Geraniaceae.

Habit and leaf form. Herbs; bearing essential oils. Annual, or biennial. Leaves basal and cauline. Plants with a basal concentration of leaves. Mesophytic, or xerophytic. Leaves opposite (cauline leaves); petiolate; gland-dotted, or not gland-dotted; aromatic, or without marked odour; simple, or compound; when compound pinnate. Leaf blades when simple, dissected (then deeply lobed); pinnately veined, or palmately veined. Leaves with stipules. Stipules interpetiolar, or intrapetiolar; membranous. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (hairs simple and/or glandular). Stem anatomy. Nodes tri-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.

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

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’, or solitary (rarely). Inflorescence (1-)2–9-flowered. Flowers in umbels. Inflorescences terminal, or axillary, or leaf-opposed; with involucral bracts, or without involucral bracts. Flowers pedicellate; bracteolate; small; regular to somewhat irregular. The floral asymmetry involving the perianth. Flowers 5 merous; cyclic. Free hypanthium absent. Hypogynous disk present; of separate members (alternating with C, around A). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous, or gamosepalous; imbricate (with valvate tips); regular; neither appendaged nor spurred; persistent; with the median member posterior. Sepals with a bluntly mucronate apex. Corolla 5; 1 -whorled; polypetalous; imbricate, or contorted; regular to unequal but not bilabiate (upper 2 members may be slightly longer than the lower 3); white, or pink, or purple, or blue; deciduous (caducous). Petals clawed. Androecium 10. Androecial sequence determinable. Androecial members all equal to markedly unequal; coherent; 1 - adelphous; 2 -whorled. Androecium including staminodes. Staminodes 5 (alternating with the fertile stamens). Stamens 5; isomerous with the perianth; alternisepalous. Anthers oblong in outline; dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 5 locular. Styles 1 (with an elongating, persistent column); attenuate from the ovary; apical. Stigmas 5; dry type; papillate; Group II type. Placentation axile. Ovules 1 per locule, or 2 per locule; pendulous, or ascending; epitropous; with ventral raphe; superposed; anatropous to campylotropous.

Fruit and seed features. Fruit non-fleshy; a schizocarp. Mericarps 5; clavate in outline, hairy; awns with long ferruginous hairs on the inner surface and short white hairs on the outer surface, spiralling and breaking away from the central axis and carrying the mericarp upwards at maturity. Seeds 1 per mericarp. Seeds clavate; endospermic (scantily), or non-endospermic; exotegmic. Cotyledons 2. Embryo straight, or curved to bent. Seedling. Germination phanerocotylar.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia.