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Monotaxis Brongn.

Ann.Sci.Nat. (Paris) p386 (1833)
Name Status

Scientific Description

Family Euphorbiaceae.

Habit and leaf form. Shrubs, or herbs; non-laticiferous and without coloured juice. Plants succulent, or non-succulent. Mesophytic, or xerophytic. Leaves small to medium-sized; alternate, or opposite; spiral, or distichous; ‘herbaceous’, or leathery, or fleshy; petiolate; non-sheathing; gland-dotted, or not gland-dotted; simple. Leaf blades entire; pinnately veined, or palmately veined. Leaves with stipules, or without stipules. Stipules small, scaly, or leafy; caducous, or 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. Male flowers without pistillodes. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes (small, dense), or in heads. Inflorescences terminal, or axillary; either sessile or pedunculate in the upper axils, male flowers usually numerous, female flowers 1 or few per cyme among the males. 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, or absent. Perianth with distinct calyx and corolla, or sepaline; 8–10, or 4–5 (when corolla absent); 1 -whorled, or 2 -whorled; when two-whorled, isomerous. Calyx 4, or 5; polysepalous, or gamosepalous; imbricate, or valvate; regular. Corolla present, or absent (sometimes, in female flowers); when present, 4, or 5; polypetalous; regular. Fertile stamens present, or absent (female flowers). Androecium 7, or 8. Androecial members free of the perianth; free of one another (if filaments interpreted as arising from an androphore), or coherent (filaments shortly connate at the base). Androecium exclusively of fertile stamens. Stamens 7, or 8; diplostemonous; erect in bud, or inflexed in bud. Anthers dehiscing via short slits (the cells minute, globular, separated by a curved, horizontal connective); 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 (depending on interpretation of partially connate styles); superior. Ovary plurilocular; 3 locular. Styles 3; free, or partially joined (connate at the base); deeply forked; apical. Stigmas 6; dry type; papillate (papillose-fimbriate); Group II type. Placentation axile, or apical. Ovules 1 per locule; pendulous; epitropous; with ventral raphe, or with dorsal raphe; arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent, or a schizocarp (globular or trigonous). Mericarps 3; 2-valved. Fruit when dehiscent, a capsule; elastically dehiscent (schizocarpic capsules often splitting elastically), or passively dehiscent. Seeds 1 per mericarp. Seeds ovoid to cylindric; endospermic. Endosperm oily. Seeds arillate. Cotyledons 2 (much longer but scarcely wider than the radicle). Embryo mostly straight (and linear). 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, South Australia, Northern Territory, and Queensland. Northern Botanical Province and South-West Botanical Province.

H.R. Coleman, 8 September 2016

Taxonomic Literature

  • Halford, David A.; Henderson, Rodney J. F. 2002. Studies in Euphorbiaceae A.L. Juss. sens. lat. 4, a revision of Monotaxis Brongn. (Acalyphoideae Ascherson, Ampereae Mull. Arg.).
  • 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..
  • Grieve, B. J.; Blackall, W. E. 1998. How to know Western Australian wildflowers : a key to the flora of the extratropical regions of Western Australia. Part II, Dicotyledons (Amaranthaceae to Lythraceae). University of W.A. Press.. Nedlands, W.A..
  • Wheeler, J. R.; Rye, B. L.; Koch, B. L.; Wilson, A. J. G.; Western Australian Herbarium 1992. Flora of the Kimberley region. Western Australian Herbarium.. Como, W.A..
  • Marchant, N. G.; Wheeler, J. R.; Rye, B. L.; Bennett, E. M.; Lander, N. S.; Macfarlane, T. D.; Western Australian Herbarium 1987. Flora of the Perth region. Part one. Western Australian Herbarium.. [Perth]..