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(Last Modified On 1/25/2013)
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(Last Modified On 1/25/2013)
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Genus
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AMARANTHUS L.
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PlaceOfPublication
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Sp. P1. 989. 1753.
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Synonym
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Bliton Adans. Fam. P1. 2:506. 1763. Bajan Adans. loc. cit. 506. 1763. Roemeria Moench, Meth. 341. 1794. Glomeraria Cav. Descr. 319. 1803. Diimeiandra Raf. Neogen. 2. 1825. Scleropus Schrad. Intd. Sem. Hort. Gott. 1835.; in Linnaea 11: Litt.-ber. 89. 1837. Dimeianthus Raf. Fl. Tell. 3:41. 1837. Amblogyna Raf. loc. cit. 42. 1837. Euxolus Raf. loc. cit. 42. 1837. Pentrius Raf. loc. cit. 42. 1837. Albersia Kunth, Fl. Berol. ed. 2. 144. 1838. Mengea Schauer, in Meyer, Nov. Acta Acad. Leop. 19: Supply. 1:405. 1843. Pyxidium Moq. in DC. Prodr. 132:262. 1849. Sarratia Moq. loc. cit. 262. 1849. Galliaria Bubani, Fl. Pyren. 1:184. 1897.
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Description
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Flowers monoecious, dioecious or polygamous, sessile or subsessile, unibracteate and bibracteolate. Sepals 3-5, rarely 1, discrete, hypogynous, concave, occasionally basally clawed, equal or subequal, membranaceous, erect and persistent in fruit. Stamens 3-5, rarely 1, hypogynous, discrete; filaments filiform; anthers 4-locellate, introrse, medially attached, oblong. Ovary ovoid to lenticular, 1-locular, 1- ovulate, the ovule campylotropous on a short exarillate funicle, the placentation basal; styles 1-3; stigmata 2-3, usually exceeding the styles. Fruit a utricle, indehiscent or circumscissile; seeds cochleate-orbiculate, smooth to minutely verrucose. Leaves alternate, entire to minutely crenulate, long-petiolate. Erect or prostrate, glabrous to pubescent annual herbs. Inflorescences of terminal and/or axillary spicate or paniculate thyrses, in Panama monoecious or polygamous with female flowers basally, hermaphroditic flowers medially, and male flowers distally, the latter tending to have longer, narrower sepals.
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Distribution
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Widespread in both temperate and tropical regions throughout the world, Amaranthus consists of perhaps fifty species. Many of them are inhabitants of open disturbed areas where they may become rather annoying weeds.
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Note
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Some are cultivated for their edible seeds and leaves, and others, with brightly colored inflorescences, are planted as ornamentals. Sauer (Ann. Missouri Bot. Gard. 37: 561-632. 1950) reports on the detailed ethnological history of the grain-amaranths. Seven species have been reported in Panama, but one, adventive on San Jose Island, apparently no longer persists.
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Reference
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Sauer (Ann. Missouri Bot. Gard. 37: 561-632. 1950)
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Key
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a. Stamens and sepals 1-3, the sepals mostly less than 1.5 mm. long; utricle rugulose. b. Inflorescences terminal and axillary; sepals of the pistillate flowers 3, the bracts about equaling them in length; stamens 3... -....-........ 1. A. VIRIDIS bb. Inflorescences all axillary; sepals of the pistillate flowers mostly 1-2, about half as long as the bracts; stamens mostly 2. - 2. A. CALIFORNICUS aa. Stamens and sepals 5, the sepals mostly more than 1.5 mm. long; utricle smooth or rugulose. c. Utricle subglobose; stylopodium circular in cross section; sepals red or purple; plants unarmed ....................................................................... 3. A. CRUENTUS cc. Utricle compressed-ovoid; stylopodium 2-3-lobulate in cross section; sepals greenish; plants armed or unarmed. d. Plants unarmed; axillary inflorescences cylindric. e. Thyrses less than 6 mm. broad; bracts of the pistillate flowers mostly shorter than the sepals, some of the sepals spatulate ........ 4. A. DUBIUS ee. Thyrses more than 6 mm. broad; bracts of the pistillate flowers mostly longer than the sepals, giving the spikes a bristly appear- ance; none of the bracts spatulate .------------------------------------ 5. A. HYBR!DUS dd. Plants armed; axillary inflorescences globose .... 6. A. sPINosus
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Note
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In addition: to the aforementioned, Johnston (in Sargentia 8:124. 1949) adds that A. retroflexus L. was collected on San Jose Island in 1945 (Erlanson 188), but was unsuccessfully searched for in 1946. I have not seen the specimen. The species is separated from the closely allied species A. hybridus by the obtuse sepals of the pistillate flowers.
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