Habit and leaf form. Trees, or shrubs, or herbs; non-laticiferous and without coloured juice. Plants succulent, or non-succulent. Herbs annual, or perennial. Mesophytic, or xerophytic. Leaves minute to large; alternate; spiral, or distichous; ‘herbaceous’, or leathery, or fleshy; petiolate; non-sheathing; gland-dotted, or not gland-dotted; simple. Leaf blades entire; palmi- or penninerved. Leaves with stipules. Stipules of WA taxa subulate, c. 1.5–3 mm long; caducous, or persistent. Leaf blade margins often dentate, or crenate. Leaves without a persistent basal meristem. Leaf anatomy. Urticating hairs present, or absent. Stem anatomy. Nodes tri-lacunar, or unilacunar. Secondary thickening developing from a conventional cambial ring, or anomalous; from a single cambial ring.
Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Unisexual flowers present. Plants monoecious, or dioecious. Male flowers without pistillodes. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in spikes, or in racemes, or in panicles, or in glomerules. Inflorescences terminal, or axillary; solitary or paired, uni- or bisexual, the bisexual inflorescences with female flowers towards the base and male flowers towards the apex; female inflorescences axillary or terminal, of 1–5 flowers within the bract; male inflorescences axillary, the small flowers clustered together in glomerules subtended by inconspicuous bracts. Flowers pedicellate (in the male inflorescence), or subsessile (in the female inflorescence); bracteate; minute to small; regular. Floral receptacle developing an androphore (stamens attached to a slightly raised receptacle). Free hypanthium absent. Hypogynous disk absent. Perianth sepaline; 3–5 (in female flowers), or 4 (in male flowers); 1 -whorled. Calyx 3–5; gamosepalous; imbricate (in female flowers), or valvate (in male flowers); regular. Fertile stamens present, or absent (female flowers). Androecium 8–12. Androecial members free of the perianth; free of one another. Androecium exclusively of fertile stamens. Stamens 8–12; diplostemonous to triplostemonous; erect in bud, or inflexed in bud. Filaments filiform or flattened. Anthers oblong to linear, pendulous and vermiform; basifixed; dehiscing via longitudinal slits; extrorse, or introrse; bisporangiate, or tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 2 carpelled, or 3 carpelled. The pistil 2 celled, or 3 celled. Gynoecium syncarpous; synovarious, or synstylovarious (depending on interpretation of partially connate styles); superior. Ovary plurilocular; 2 locular, or 3 locular. Styles 2, or 3; free, or partially joined; forked to more than 4-branched (to laciniate), or simple (rarely); apical. Stigmas 4–12 (? or more); dry type; papillate, or non-papillate; Group II type. Placentation axile, or apical. Ovules 1 per locule; pendulous; epitropous; with ventral raphe, or with dorsal raphe; arillate, or non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; a schizocarp (usually 3-lobed, dehiscing septicidally). Mericarps 3. Fruit elastically dehiscent (schizocarpic capsules often splitting elastically), or passively dehiscent. Seeds 1 per mericarp. Seeds ellipsoid or subglobose; endospermic. Endosperm oily. Seeds arillate, or non-arillate. Cotyledons 2 (broad); flat. Embryo straight, or curved. Testa crustaceous. Seedling. Germination phanerocotylar, or cryptocotylar.
Physiology, biochemistry. Mustard-oils present, or absent.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, or Queensland, or New South Wales. Northern Botanical Province.
Additional characters Female flowers 1–5, enclosed within a toothed or lobed, accrescent bract.
Forster, Paul I. (1994). A taxonomic revision of Acalypha L. (Euphorbiaceae) in Australia.
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