Pseudanthus A.Spreng.

Scientific Description

Family Euphorbiaceae.

Habit and leaf form. Shrubs; non-laticiferous and without coloured juice. Plants succulent, or non-succulent. Mesophytic, or xerophytic. Leaves minute to small; alternate, or opposite; spiral, or distichous; leathery (midrib and margins prominent and thickened on the lower surface); shortly petiolate to sessile; non-sheathing; gland-dotted, or not gland-dotted; simple. Leaf blades entire; pinnately veined, or palmately veined. Leaves with stipules. Stipules small, subulate or rarely with a broadened base; persistent. 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. Female flowers solitary, or aggregated in ‘inflorescences’ (then in small clusters). Male flowers solitary, or aggregated in ‘inflorescences’ (then in small clusters with the females); with pistillodes (rudimentary ovary small). Entomophilous.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary. Inflorescences axillary; not pseudanthial (usually), or pseudanthial (in P. pimeleoides). Flowers pedicellate to sessile; bracteate, or ebracteate; minute to medium-sized; regular. Floral receptacle developing an androphore, or with neither androphore nor gynophore (? depending on interpretation). Free hypanthium absent. Hypogynous disk present, or absent. Perianth sepaline; 3–6; 1 -whorled. Calyx 3–6; 1 -whorled; polysepalous; regular. Fertile stamens present, or absent (female flowers). Androecium 3, or 6, or 9–18. Androecial members branched, or unbranched; free of the perianth; free of one another, or coherent (filaments of P. pimeleoides partially fused to central disc, while in P. virgatus and P. nematophorus the outer filaments are free but the inner are connate at the base). Androecium exclusively of fertile stamens. Stamens 3, or 6, or 9–18; isomerous with the perianth to polystemonous; erect in bud, or inflexed in bud. Anthers opening by valves, the cells distinct with a long, curved connective between; extrorse; bisporangiate, or tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 2 carpelled, or 3 carpelled. The pistil 1–3 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary plurilocular, or unilocular (the septa very early obliterated); 2–3 locular, or 1 locular (finally). Gynoecium stylate (then greatly reduced), or non-stylate (if carpel interpreted as possessing sessile stigmatic branches). Styles 2, or 3; apical. Stigmas 2, or 3 (large, thick); dry type; papillate, or non-papillate; Group II type. Placentation axile, or apical. Ovules 2 per locule (in early stages), or 1 per locule (by abortion); pendulous; epitropous; with ventral raphe, or with dorsal raphe; when two, collateral; arillate; orthotropous, or anatropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule (ovoid, opening by 4–6 valves); 1 celled; 1 seeded. Seeds oblong, cylindric; endospermic. Endosperm oily. Seeds arillate. Cotyledons 2 (longer but scarcely wider than the radicle). Embryo linear, straight, or curved. Testa smooth. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Mustard-oils present, or absent.

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia and South Australia. South-West Botanical Province.

Additional comments. Further study of specimens is required before the proposal by Radcliffe-Smith (1993) to subsume Stachystemon under Pseudanthus can be accepted (P.G. Wilson, pers. comm.).