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  1. Family: Acanthaceae Juss.
    1. Duosperma Dayton

      1. This genus is accepted, and its native range is Tropical & S. Africa.


    Acanthaceae (part 2), Kaj Vollesen. Flora of Tropical East Africa. 2008

    Perennial or shrubby herbs or shrubs, with usually conspicuous linear cystoliths (especially on calyx); stems terete to distinctly quadrangular; bark on older branches usually peeling off in flakes or strips
    Leaves opposite, with strong unpleasant smell when crushed; basal part of petiole forming a stipule-like sheath around the stem
    Flowers subsessile or petiolate, solitary or in condensed axillary cymes which sometimes merge into large panicles; bracteoles usually large and conspicuous, often foliaceous
    Calyx leathery, 5-lobed, fused in basal part, splitting in fruit; lobes lanceolate to triangular, with strong rib-like central vein and with scarious margins, dorsal lobe usually distinctly longer and wider than the rest, 2 ventral lobes fused higher up
    Corolla contorted in bud, distinctly 2-lipped; tube cylindric at base, widening into a dictinct throat which is hairy ventrally; upper lip 2-lobed, erect, sometimes slightly hooded, lower lip 3-lobed, deflexed, lobes all similar, but wider in lower lip, lower lip pleated at base, with or without long stiff hairs
    Stamens 4, inserted just inside cylindric part of tube, didynamous (longer pair 1–2 mm longer than short pair), held under upper lip, the two short stamens occasionally reduced to staminodes; filaments fused with tube, fused part running like two puberulous longitudinal ridges to base of tube, free part of each long and short filament fused at base; anthers 2-thecous, thecae oblong, rounded or apiculate at both ends, never with spurs
    Ovary with 1–2 ovules per locule.
    Style filiform, with upwardly directed hairs.
    Stigma lobes 2, linear, equal or dorsal about half the length of ventral
    Capsule (1–)2-seeded, ellipsoid-obovoid, woody, glossy, laterally compressed, usually glabrous, valves sulcate dorsally; retinaculae strong, hooked
    Seed discoid, ovoid to orbicular in outline, with hygroscopic hairs.
    Duosperma is morphologically very similar to Dyschoriste and Hygrophila but palynological work (Vollesen l.c.) strongly implies that it is closer to Mellera, Mimulopsis and Eremomastax. It differs from Dyschoriste and Hygrophila in the laterally compressed 2-seeded capsule and in having a style with both stigma lobes well-developed. The large conspicuous bracteoles also provide a useful spot-character.  The capsules usually persist on the plant until next rainy season. The apical part (base of style) is thickened and slightly bulbous and only tardily dehiscent.
    Range: 26 species in eastern and southern tropical Africa from Somalia and S Ethiopia to Botswana and Angola. One species extends to Yemen. Particularly diverse from central and SW Tanzania into N Zambia and SE Congo.



    Native to:

    Angola, Botswana, Caprivi Strip, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Northern Provinces, Somalia, Sudan, Tanzania, Tennessee, Uganda, Yemen, Zambia, Zaïre, Zimbabwe

    Accepted Species


    Other Data

    Duosperma Dayton appears in other Kew resources:


    First published in Rhodora 47: 262 (1945)

    Accepted by

    • Govaerts, R. (2000). World Checklist of Seed Plants Database in ACCESS D: 1-30141.


    Flora of Tropical East Africa

    • Vollesen K.B. 62: 289 (2006)
    • Dyer, Gen. S. Afr. Fl. Pl. 1: 587 (1975)
    • Brummitt K.B. 29: 411 (1974)
    • Rhodora 47: 262 (1945)


    Flora of Tropical East Africa
    Flora of Tropical East Africa

    Kew Backbone Distributions
    The International Plant Names Index and World Checklist of Selected Plant Families 2020. Published on the Internet at and
    © Copyright 2017 World Checklist of Selected Plant Families.

    Kew Names and Taxonomic Backbone
    The International Plant Names Index and World Checklist of Selected Plant Families 2020. Published on the Internet at and
    © Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families.