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20. Leucas Burm. ex R. Br., Prodr. Fl. Nov. Holland. 504. 1810. Benth. in DC., Prodr. 12: 523. 1848; Hook. f., Fl. Brit. Ind. 4: 680. 1885; Briquet in Engler & Prantl, Nat. Pflanzenfam. ed. 1, 4, 3A: 250. 1896; Mukerjee in Rec. Bot. Surv. Ind. 14, 1: 162. 1940; Sebald, in Stuttg. Beitr. Naturk. ser. A, 341. 1980; Rech. f. Fl. Iran. 150: 318-320. 1982.
I.C. Hedge
Annual or perennial herbs with a pilose to villous eglandular indumentum of simple hairs. Leaves undivided, entire to crenate-serrate, petiolate at least on lower leaves, usually gland-dotted. Verticillasters many-flowered, distant from each other, borne in axils of upper leaves. Bracts numerous, subulate to ovate-lanceolate, shorter than to as long as calyces. Flowers white, sometimes with cream, rose or green markings. Calyx with 10 often ribbed veins, tubular, straight or curved; mouth truncate to prominently oblique, pilose to vinous at throat; teeth 8-10, equal or unequal. Corolla rather small, bilabiate; tube included in calyx, internally oblique-annulate or not; upper lip hooded or ± straight, densely white-bearded; lower lip with a median lobe clearly larger than laterals, usually much longer than upper lip. Stamens 4, didynamous, included within corolla upper lip; thecae 2-locular, eventually confluent. Style shortly 2-lobed. Nutlets 4, oblong, trigonous, obtuse to truncate-rounded at apex.
A palaeotropical genus of about 80 species with two main centres: one in Africa, especially east tropical Africa; the other in the Indian subcontinent. Most of our species are quite clear-cut.
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| 1 |
Annuals |
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(2) |
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Perennials |
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(5) |
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| 2 (1) |
Throat of calyx prominently hairy with long hairs |
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(3) |
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Throat of calyx glabrous or somewhat pilose with very short hairs |
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(4) |
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| 3 (2) |
Calyces prominently curved, some ± reflexed; calyx teeth upto 2.5 mm; bracts not imbricate |
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7 Leucas nutans |
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Calyces slightly curved, not reflexed; calyx teeth upto 1 mm; bracts imbricate, numerous |
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6 Leucas cephalotes |
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| 4 (2) |
Stems with short spreading hairs; bracts c 1/2 length of calyces |
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5 Leucas aspera |
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Stems with very short ± retrorse hairs; bracts more than 1/2length of calyx |
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4 Leucas urticifolia |
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| 5 (1) |
Leaves linear, entire-margined; calyces glabrous or with few hairs |
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3 Leucas hyssopifolia |
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Leaves ovate; calyces with a prominent indumentum |
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(6) |
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| 6 (5) |
Stem indumentum of retrorse hairs; plant greyish green |
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1 Leucas mollissima |
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Stem indumentum of spreading or antrorse hairs; plant white lanate |
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2 Leucas lanata |
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Lower Taxa
Related Synonym(s):
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