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54. Isodon (Schrad. ex Benth.) Spach, Hist. Nat. Veg. Phanerogam. 9: 162. 1840. Codd, Notes on the genus Isodon, in Taxon 17: 239. 1968; Codd, The genus Isodon (Schrad. ex Benth.) Spach in Africa and a new genus Rabdosiella Codd (Lamiaceae), in Bothalia 15, 1 & 2: 7-10. 1984; Hara, Isodon in Comments on East Asiatic plants 17 in Journ. Jap. Bot. 60, 8: 232- 237. 1985; Hsi-wen Li, Taxonomic review of Isodon, In Journ. Arn. Arb. 69: 289-400. 1988.
I.C. Hedge
Elsholtzia sect. Rabdosia BlumePlectranthus* auctt. p.p., Hook. f.Rabdosia (Blume) Hassk.
Perennial or annual herbs, subshrubs or shrubs, with an indumentum of simple or dendroid hairs or subglabrous. Leaves undivided, crenate to serrate, petiolate or sessile. Inflorescence of cymes, usually in spreading panicles. Flowers violet blue pink or whitish. Calyx indistinctly bilabiate; teeth (in ours) subequal; upper lip 3-lobed; lower lip 2-lobed; calyx enlarged and curved, often deflexed, in fruit. Corolla bilabiate; upper lip 2-4-fid often recurved; lower lip entire, cucullate longer than upper; tube exserted, straight or curved, gibbous or not at base. Stamens 4, declinate, didynamous; filaments free, not toothed, glabrous; thecae unilocular by fusion, glabrous. Style subequally bind at apex. Nutlets ovoid or oblong, smooth to granulate, often mucilaginous on wetting.
Up to c. 100 species in Asia, with a major centre in China. Although Isodon is accepted here as independent from Plectranthus, the two genera are very closely allied and some authors prefer to regard Isodon either as a synonym or else as an infra-generic taxon of Plectranthus. The main distinguishing feature of Isodon is its indistinctly bilabiate calyx with 5 subequal teeth; in contrast Plectranthus has a calyx with 1 large ovate uppermost lobe and 4 narrow triangular lower teeth.
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Shrub with fine stellate-dendroid hairs; leaves ± rugose |
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1 Isodon rugosus |
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Herbs, sometime woody at base, with simple hairs; leaves not rugose |
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(2) |
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| 2 (1) |
Calyx 1-1.5 mm in flower with obtuse teeth; corolla tube c. 5 mm, not gibbous at base |
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2 Isodon lophanthoides |
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Calyx 2 mm in flower with ± acute teeth; corolla tube c. 3 mm, clearly gibbous at base |
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3 Isodon coetsa |
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Lower Taxa
Related Synonym(s):
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