Dimorphocalyx Thwaites

Scientific Description

Family Euphorbiaceae.

Habit and leaf form. Trees; laticiferous (latex non-toxic). Plants succulent, or non-succulent. Mesophytic, or xerophytic. Leaves medium-sized to large; alternate; spiral, or distichous; ‘herbaceous’, or leathery, or fleshy; petiolate; non-sheathing; gland-dotted, or not gland-dotted; simple. Leaf blades entire; pinnately veined. Leaves with stipules. Stipules scaly, or leafy; caducous. 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 dioecious, or monoecious (rarely). Female flowers aggregated in ‘inflorescences’, or solitary (sometimes). Male flowers aggregated in ‘inflorescences’; without pistillodes. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’, or solitary; in cymes, or in racemes. Inflorescences axillary. Flowers bracteate, or ebracteate; minute to small; regular. Floral receptacle developing an androphore, or with neither androphore nor gynophore (? depending on interpretation). Free hypanthium absent. Hypogynous disk present; annular. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (lobed or cupular in male flowers; almost free in female flowers); regular; accrescent. Corolla 5; polypetalous; regular; glabrous abaxially; glabrous adaxially. Fertile stamens present, or absent (female flowers). Androecium 7–20. Androecial members branched, or unbranched; free of the perianth; free of one another (if filaments interpreted as arising from an androphore), or coherent (the outermost filaments partly connate and the innermost almost completely connate into a column). Androecium exclusively of fertile stamens. Stamens 7–20; diplostemonous to polystemonous; erect in bud, or inflexed in bud. Anthers dorsifixed; dehiscing via longitudinal slits; extrorse, or introrse; bisporangiate, or tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary plurilocular; 3 locular. Styles 3; free, or partially joined; forked; apical. Stigmas 6; 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; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; a schizocarp (capsular). Mericarps crustaceous, 2-valved. Fruit elastically dehiscent (schizocarpic capsules often splitting elastically), or passively dehiscent. Seeds 1 per mericarp. Seeds ovoid; endospermic. Endosperm oily. Cotyledons 2 (usually wider than the radicle). Embryo straight, or curved. 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, Queensland, and New South Wales. Northern Botanical Province.