Pomax DC.
Prodr. 4:615 (1830)

Name Status: Current
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Scientific Description
H.R. Coleman, Thursday 8 September 2016

Common name. Pomax. Family Rubiaceae.

Habit and leaf form. Shrubs (shrublets), or herbs. Herbs perennial. Young stems cylindrical. Helophytic, or mesophytic, or xerophytic. Leaves opposite; petiolate to subsessile; connate (via the stipules), or not connate; gland-dotted, or not gland-dotted; simple; epulvinate. Leaf blades entire; one-veined, or pinnately veined; cross-venulate. Leaves with stipules. Stipules scarcely connate with the leaf base; with colleters (secreting mucilage), or without colleters. Leaf blade margins entire, or serrate. Leaves without a persistent basal meristem. Domatia recorded, or not recorded; represented by pits, or pockets, or hair tufts. Leaf anatomy. Hairs present, or absent. Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite (protandrous). Plants homostylous, or heterostylous. Entomophilous. Pollination mechanism conspicuously specialized (with passive pollen presentation involving stylar modification), or unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. The terminal inflorescence unit cymose. Inflorescences terminal; usually an umbellate thyrse, with 3–11 flower-like cymules on a long stalk, each of 2–4 flowers connate to one another; with involucral bracts (involucre funnel-shaped, sepaloid). Flowers small; regular; 3–5 merous; cyclic; tetracyclic. Free hypanthium present, or absent (depending on interpretation). Perianth with distinct calyx and corolla; 6–10; 2 -whorled; the two whorls isomerous. Calyx 3–5; 1 -whorled; polysepalous, or gamosepalous; entire, or lobed; open in bud; regular; persistent. Corolla 3–5; 1 -whorled; gamopetalous. Corolla lobes markedly shorter than the tube. Corolla imbricate, or valvate, or contorted; funnel-shaped; regular; pink to purple, or red; spurred, or not spurred; deciduous. Androecium 3–5. Androecial members adnate (to the corolla tube, filaments almost free); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 3–5. Staminal insertion near the base of the corolla tube. Stamens becoming exserted; isomerous with the perianth; oppositisepalous; filantherous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged. The anther appendages apical. Pollen shed in aggregates, or shed as single grains; if aggregated, in tetrads. Gynoecium 2 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious; inferior. Ovary unilocular; 1 locular. Epigynous disk present. Gynoecium stylate. Styles 1; attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary at anthesis to much longer than the ovary at anthesis. Stigmas 2 (filiform); wet type, or dry type; papillate, or non-papillate; Group II type and Group IV type. Placentation parietal. Ovules in the single cavity 1; pendulous, or horizontal, or ascending; anatropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent. Gynoecia of adjoining flowers combining to form a multiple fruit (flowers in each head fused by their ovaries to form a usually 3-locular compound fruit, dehiscing by an almost round apical lid). Fruit 1–3 seeded. Seeds 1 per locule. Seeds coffee bean-shaped; endospermic, or non-endospermic. Endosperm ruminate, or not ruminate; if present, oily. Cotyledons 2. Embryo straight, or curved. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated, or not found.

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, and Australian Capital Territory.

Etymology. From the Greek for "lid, cover"; refers to the lid of the compound fruit.

Taxonomic Literature

  • Grieve, Brian J.; Blackall, William E. (1982). How to know Western Australian wildflowers : a key to the flora of the extratropical regions of Western Australia. Part IV. University of W.A. Press. [Perth].