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Project Name Data (Last Modified On 6/14/2013)

Flora Data (Last Modified On 6/14/2013)
Genus Acanthospermum Schrank
PlaceOfPublication P1. Rar. Hort. Monac. tab. 53. 1819.
Note TYPE: A. brasilum Schrank = A. australe (Loefl.) Kuntze.
Description Annual herbs; stems dichotomously branched, pubescent. Leaves opposite, subentire to pinnatifid. Inflorescence of solitary heads in the axils and forks of the stem. Heads radiate; involucre biseriate, the outer bracts 4-6, elliptic to ovate, herbaceous, the inner bracts of the same number as the ray achenes and closely enveloping them; receptacle small, convex, paleaceous; ray florets carpellate, fertile, uniseriate, 5-8, the corollas elliptic to ovate, pale yellow, the apex emarginate or tridenticulate, the tube as long as or much shorter than the limb; disc florets perfect, 3-30, the corollas yellow with a short cylindrical tube, the throat cylindric-funnelform or campanulate, 5-lobed, the anthers barely cordate to cordate-sagittate, the appendage ovate, obtuse, and somewhat inflexed, the style clavate, obtuse, undivided, hispidulous, the ovary sterile, pappus absent. Fruit cuneate or oblong-fusiform, rarely trigonous-turbinate, weakly or strongly laterally compressed, more or less densely echinate on the whole surface, the angles with straight or usually uncinate prickles. Chromosome numbers n = 10, 11.
Habit herbs
Distribution This is a genus of 6 species distributed primarily throughout Latin America.
Note One species, A. hispidum, has been introduced to many ports of entry throughout the world. Acanthospermum is a close relative of Melampodium, a genus also found in Panama. Both taxa have perfect but sterile disc florets and involucral bracts of the inner series that enclose single ray achenes. The most important feature distinguishing the two genera comes from the fruits which are spiny in Acantho- spermum and smooth, ribbed, or sculptured in Melampodium
Reference Blake, S. F. 1921. Revision of the genus Acanthospermum. Contr. U.S. Natl. Herb. 29: 383-392. Stuessy, T. F. 1970. The genus Acanthospermum (Compositae-Heliantheae- Melampodinae): taxonomic changes and generic affinities. Rhodora 72: 106-109.
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