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Pelargonium Aiton
Hort.Kew. 2:417 (1789)

Name Status: Current

Scientific Description
H.R. Coleman, Friday 3 October 2008

Family Geraniaceae.

Habit and leaf form. Herbs, or shrubs; bearing essential oils. Herbs annual, or perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Shrubs leptocaul, or pachycaul. Mesophytic, or xerophytic. Leaves alternate, or opposite; petiolate; non-sheathing; gland-dotted, or not gland-dotted; aromatic (via capitate glands); simple. Leaf blades dissected (lobed to deeply dissected), or entire; broadly ovate; pinnately veined, or palmately veined; cordate. Leaves with stipules. Stipules interpetiolar, or intrapetiolar; membranous. Leaf blade margins crenate, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present. 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’; in umbels. Inflorescences terminal; arranged in cincinni; with involucral bracts, or without involucral bracts. Flowers pedicellate, or sessile; bracteolate; small, or medium-sized; somewhat irregular. The floral asymmetry involving the perianth and involving the androecium. Flowers 5 merous; cyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (basally); imbricate (with valvate tips); regular; basally appendaged to spurred (the posterior member prolonged into a tube adnate to the pedicel); persistent; with the median member posterior. Corolla 5; 1 -whorled; polypetalous; contorted (usually); unequal but not bilabiate (the 2 posterior members larger than the 3 anterior ones); white, or pink to purple (with darker markings); deciduous (caducous). Petals clawed. Corolla members bilobed, or entire. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members markedly unequal; coherent; 1 - adelphous (basally connate into a tube). Androecium including staminodes. Staminodes 2–7. Stamens 3–8; alternisepalous. Filaments elliptic. 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 2 per locule; ascending; epitropous; with ventral raphe; superposed; anatropous to campylotropous.

Fruit and seed features. Fruit non-fleshy; a schizocarp. Mericarps 5; ellipsoid, hirsute, breaking away elastically from the base at maturity; the curved awns hairy from the central axis. Seeds 1 per mericarp. Seeds more or less ellipsoid; 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. Australian states and territories: Western Australia, South Australia, New South Wales, and Victoria.

Keys to Pelargonium Aiton