Acidonia L.A.S.Johnson & B.G.Briggs
Bot.J.Linn.Soc. p175 (1975)
Friday 3 October 2008
Habit and leaf form. Erect shrubs (bark smooth, compact); evergreen. Young stems moderately to densely hairy. To 0.6–3 m high. Mesophytic, or xerophytic. Not heterophyllous. Leaves medium-sized; alternate; usually spiral; leathery, or fleshy; sessile; non-sheathing; not twisting; simple; epulvinate. Leaf blades entire; flat; linear; linear; with obscure venation. Mature leaf blades adaxially glabrous; abaxially glabrous. Leaves without stipules. Leaf blade margins entire. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous, or cheiropterophilous, or pollinated by unusual means.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence few-flowered (1–4 flowered). Flowers in racemes, or in spikes. Inflorescences axillary; lateral, abbreviated, anauxotelic; flowers subtended by scale leaves. The fruiting inflorescence not conelike. Flowers pedicellate; bracteate; small to medium-sized; regular; 4 merous; cyclic; tetracyclic. Floral receptacle developing a gynophore, or with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present; extrastaminal; of separate members (comprising 4 equal glands). Perianth of ‘tepals’; 4; 1 -whorled; free; moderately hairy; yellow. Perianth members entire. Androecial members definite in number. Androecium 4. Androecial members partly adnate (to tepals); all equal; free of one another; 1 -whorled. Stamens 4; all more or less similar in shape; isomerous with the perianth. Anthers all alike; basifixed; slightly incurved (and flattened); non-versatile; dehiscing via longitudinal slits; introrse; four locular; tetrasporangiate; appendaged (connective slightly wider than loculi and extending beyond them as a rounded, slightly concave appendage). Gynoecium 1 carpelled. The pistil 1 celled. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic. Style straight (but recurved at tip). Carpel 2 ovuled. Placentation marginal, or apical. Ovary sessile (and contracted at base). Styles becoming exserted. Ovules funicled, or sessile; non-arillate; orthotropous, or anatropous, or amphitropous, or hemianatropous.
Fruit and seed features. Fruit 4–4.5 mm long; fleshy. The fruiting carpel indehiscent; drupaceous (the pyrene compressed-ellipsoidal). Endocarp subtransversely ribbed. Fruit 1 seeded. Seeds endospermic. Embryo well differentiated. Cotyledons 2. Embryo straight.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia. South-West Botanical Province. Darling district: Margaret River to Albany, within 50 km of the coast. A genus of 1 species; 1 species in Western Australia.
Etymology. From the Greek for "a point", alluding to the connective appendage, and the ending -onia to suggest affinity with Persoonia.
Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 2, dicotyledons. Australian Biological Resources Study. Canberra.