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This genus is accepted, and its native range is Tropical & S. Africa.
Duosperma crenatum (Lindau) P.G. Meyer

[FSOM]

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit
Shrubs or subshrubs
Morphology Leaves
Leaves entire or crenate-dentate with truncate apex
Morphology Reproductive morphology Inflorescences
Flowers solitary or clustered at upper nodes, subtended by leaf-like bracts and bracteoles
Morphology Reproductive morphology Flowers Calyx
Calyx of 4 lobes, upper and lower lobes relatively wide, the lower one 2-fid, lateral lobes small, linear
Morphology Reproductive morphology Flowers Corolla
Corolla ± 2-lipped
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens 4; anthers 2-celled
Morphology Reproductive morphology Fruits
Capsule 2-seeded
Morphology Reproductive morphology Seeds
Seeds flat, orbicular, with mucilaginous hairs especially along the margin.
Distribution
Genus of some 25 species in tropical and southern Africa, and in Yemen.

[FTEA]

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

Morphology General Habit
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
Morphology Leaves
Leaves opposite, with strong unpleasant smell when crushed; basal part of petiole forming a stipule-like sheath around the stem
Morphology Reproductive morphology Flowers
Flowers subsessile or petiolate, solitary or in condensed axillary cymes which sometimes merge into large panicles; bracteoles usually large and conspicuous, often foliaceous
Morphology Reproductive morphology Flowers Calyx
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
Morphology Reproductive morphology Flowers Corolla
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
Morphology Reproductive morphology Flowers Androecium Stamens
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
Morphology Reproductive morphology Flowers Gynoecium Ovary
Ovary with 1–2 ovules per locule.
Morphology Reproductive morphology Flowers Gynoecium Style
Style filiform, with upwardly directed hairs.
Morphology Reproductive morphology Flowers Gynoecium Stigma
Stigma lobes 2, linear, equal or dorsal about half the length of ventral
Morphology Reproductive morphology Fruits
Capsule (1–)2-seeded, ellipsoid-obovoid, woody, glossy, laterally compressed, usually glabrous, valves sulcate dorsally; retinaculae strong, hooked
Morphology Reproductive morphology Seeds
Seed discoid, ovoid to orbicular in outline, with hygroscopic hairs.
Note
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.
Distribution
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

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.

Literature

Flora of Somalia

  • Flora Somalia, Vol 1, (1993) Author: by M. Thulin [updated by M. Thulin 2008]
  • Vollesen in Kew Bull. 61: 289–351 (2006).

Flora of Tropical East Africa

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

Flora of Somalia
Flora of Somalia
http://creativecommons.org/licenses/by-nc-sa/3.0

Flora of Tropical East Africa
Flora of Tropical East Africa
http://creativecommons.org/licenses/by-nc-sa/3.0

Kew Backbone Distributions
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0