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(Last Modified On 10/29/2012)
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(Last Modified On 10/29/2012)
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Genus
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COSTUS L.
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PlaceOfPublication
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Sp. P1. 2. 1753.
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Synonym
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Banksea Koenig, in Retz. Observ. 3:75. 1783. Pyxa Noronha, Verh. Bat. Genootsch. 54:3. 1791. Hellenia Retz. Observ. 6:18. 1791. Tsiana Gmel. Syst. 9. 1791. Planera Giseke. Prael. 205. 1792. Glissanthe Salisb. Trans. Hort. Soc. Lond. 1:279. 1812. Jacuanga Lestiboud. Ann. Sci. Nat. Bot. II. 15:329, 341. 1841. Cadalvena Fenzl. Sitzungsber. Akad. Wien 51:139. 1863.
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Description
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Rhizomatous perennial herbs of moderate to massive stature with unbranched stems (in Panama); leaves spiral, with closed, ligulate sheaths; inflorescence termi- nating the leafy stem (in Panama, elsewhere occasionally on special scapes directly from the rhizome), spiciform, cone-like, with conspicuous persistent imbricated bracts subtending one or few showy or rather inconspicuous flowers; calyx more or less equally 3-lobed, persistent; corolla somewhat unequally 3- lobed; stamen 1, conspicuously petalaceous; labellum (anterior staminodium) at least equalling and frequently far surpassing the corolla; ovary inferior, 3-celled, containing numerous ovules; fruit a tardily dehiscent, somewhat fleshy capsule.
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Key
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a. All bracts with conspicuous foliaceous apical appendages. b. Bracts green or reddish within at the base; flowers 8-13 cm. long, the labellum very conspicuous, greatly surpassing the corolla and stamen. c. Plants very conspicuously ferruginous-hirsute; stems somewhat spiral, relatively slender; bracts lax and membranaceous, usually green within at anthesis; corolla pale yellow to nearly white; labellum yellow, usually without markings, widely spreading 1. C. VILLOSISSIMUS cc. Plants softly puberulent or pilosulose to essentially glabrous; stems straight and relatively stout; bracts turgid and subcoriaceous, usually reddish within at anthesis; corolla pale pinkish yellow to nearly white; labellum pinkish yellow with darker orange or yellow markings, sharply reflexed -2. C. FRIEDRICHSENII bb. Bracts deep red or pink throughout; flowers 3-5 cm. long, the labellum rather inconspicuous, about as long as the corolla and stamens; plants softly ferruginous-puberulent to nearly glabrous - 3. C. LIMA aa. Bracts without foliose apical appendages, or only the lowermost some- what leaf-like. b. Flowers 7-10 cm. long, the labellum very conspicuous and spreading, reddish or purplish orange with showy pale yellow veins; plants massive; the stems stout and usually quite straight, the leaves nar- rowly elliptic to oblanceolate, the upper 30-40 cm. long -4. C. LAEVIS bb. Flowers 3-5 cm. long, the labellum essentially similar to the petals or somewhat less conspicuous, not venose; plants smaller, the stems relatively slender and usually somewhat spiral, the upper leaves 8-20 (rarely 30) cm. long. c. Bracts with the margins densely ciliate, otherwise minutely puberulent to glabrous, usually bright red with a conspicuous yellow callus, rarely orange or greenish; flowers red or reddish orange; leaves obovate or oblanceolate, gradually narrowed toward the base - _ - - _ - - 5. C. RUBER cc. Bracts puberulent to glabrous, but the margins not ciliate. d. Bracts and flowers red; leaves broadly obovate-oval, rather ob- scurely subcordate-auriculate at the base; plants wholly gla- brous - - _ 6. C. SPIRALIS (63) [ VOL. 32 64 ANNALS OF THE MISSOURI BOTANICAL GARDEN dd. Bracts and flowers yellow or orange, very rarely red; leaves obtuse or rounded at the base. e. Bracts broadly obtuse or rounded throughout, with a more or less conspicuous linear callus; spikes relatively compact. f. Leaves obovate to oblanceolate, broadest distinctly above the middle, densely ciliate on the margins, otherwise gla- brous, the sheaths minutely puberulent to glabrous; spikes usually 4-5 cm. thick, cylindric or subcylindric and much longer than broad _ - _-- 7. C. SPICATUS* ff. Leaves elliptic, broadest at about the middle, generally puberulent beneath, particularly the midrib, rarely gla- brate, the margins not ciliate, the sheaths rather sparsely spreading-villous, infrequently glabrate; spikes usually 1.5- 2.5 cm. thick, broadly ovoid - 8. C. NUTANS ee. Bracts rather narrowly acute, without a callus; spikes rela- tively loose, broadly ovoid, 4.5-5.0 cm. thick; leaves oblong- oblanceolate, broadest toward the tip, generally puberulent beneath, particularly the midrib, the sheaths puberulent or pilosulose -9. C. SCABER*
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Note
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*C. spicatus and C. scaber apparently hybridize with C. nutans.
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