(Last Modified On 3/18/2013)
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(Last Modified On 3/18/2013)
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Genus
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Alchornea Sw.
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PlaceOfPublication
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Prodr. 98, 1788
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Reference
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Fl. Ind. Occ. 2: 1153, t. 24, 1800.
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Description
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Trees or shrubs; dioecious (in Panamanian species); indumentum of simple or stellate trichomes. Leaves alternate, petiolate, inconspicuously stipulate; blades pinnately or palmately veined (often triplinerved), commonly with glandular spots near the base, generally dentate. Inflorescences axillary, of spiciform racemes, the j racemes often compound; bracts eglandular, each subtending 1-3 9 or 1-several d flowers. Staminate flowers subsessile with calyx splitting at anthesis into 2-5 valvate lobes; petals absent; disc central, confluent with bases of stamens; stamens (in local species) usually 8, in 2 whorls of 4, the filaments short, the anthers dehiscing introrsely and longitudinally; pollen grains spheroidal, 3-colporate, colpi operculate; pistillode absent. Pistillate flowers sessile to short-pedicellate; calyx- lobes usually 4, imbricate; petals absent; disc obsolete; ovary of 2 carpels, ovules 1 per locule, the styles elongated, free, undivided. Fruits capsular, dicoccous, the columella persistent; seeds tuberculate, ecarunculate, with prominent ventral raphe, endosperm present, the cotyledons broad, thin, not curved.
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Habit
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Trees or shrubs
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Note
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In the narrow circumscription of Pax and Hoffmann [Pflanzenreich 63 (IV, 147, VII): 220, 1914], Alchornea comprises about 50 species, the majority of these American. As shown by Punt (Wentia 7: 82, 1962), Alchornea closely resembles such South American genera as Aparisthmium and Conceveiba in its operculate pollen grains. Critical studies may show, therefore, that Mueller (in DC., Prodr. 15(2): 899 et seq., 1866) was justified in defining the limits of Alchornea broadly. The available Panamanian collections of Alchornea are inadequate to serve as the basis for a satisfactory treatment of the taxa. Four different species appear to be recorded at present, but additional Colombian species may be expected in Darien.
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Key
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a. Leaves (except on sprout-shoots) not over 20 cm long, glabrescent, with veinlet reticulum moderately prominulous beneath. b. Leaves rigidly chartaceous to coriaceous; basal foliar glands mostly 2-4. c. Staminate spikes unbranched; leaf vein axils not barbate beneath -.. . 1. A. costaricensis cc. Staminate spikes compound; leaf vein axils distinctly barbate beneath -.. 2. A. latifolia bb. Leaves membranous to thinly chartaceous; basal foliar glands mostly more than 4 . ........... 3. A. glandulosa aa. Leaves 24 cm long or more, stellate-pubescent beneath, with veinlet reticulum corrugate-impressed above and distinctly raised beneath . 4. A. grandis
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