楼梯草属

9. Elatostema J. R. Forster & G. Forster, Char. Gen. Pl. 53. 1775. [nom. cons.] 楼梯草属 lou ti cao shu Lin Qi (林祁); Ib Friis, C. Melanie Wilmot-Dear Small shrubs, subshrubs, or herbs, without stinging hairs. Leaves apparently alternate, distichous; nanophylls present or absent, opposite to normal leaves; stipules 2; leaf blade 3-veined, one or both major lateral veins sometimes inserted above the base, or pinnately veined, base asymmetric, cystoliths linear or fusiform. Inflorescences usually pedunculate, mostly many-flowered or rarely 1-3-flowered discoid capitula, capitula usually 2-valved, each valve with several glomerules of several flowers and subtended by a few bracteoles; unisexual (plants monoecious or dioecious); male inflorescences usually with discoid receptacle (pyriform young receptacle in E. brachyodotnum and E. ficoides), rarely cymose; female ones with discoid receptacle and bracteoles along margin. Male flowers: perianth lobes 4 or 5, elliptic, connate at base, usually corniculate or short horned below apex; stamens as many as and opposite to perianth lobes; filaments of stamens inflexed in bud; rudimentary pistil small or absent. Female flowers: perianth lobes 4 or 5, or reduced, less than 1/2 length of ovary, free or connate at base, not corniculate at apex; staminodes 3-5, linear. Ovary straight, ellipsoid; style absent; stigma penicillate; ovule orthotropous. Achenes ovoid or ellipsoid, slightly flattened, mostly longitudinally 6-10-ribbed, rarely smooth or tuberculate.About 300 species: tropical and subtropical Africa, Asia, and Oceania; 146 species (108 endemic) in China. 【引自：Flora of China】