384 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
easily become entangled in the wool of sheep and are said to cause 
financial loss in the Southern States in this way, by lowering the 
quality of the wool. A third species, A. humile, originally described 
from Santo Domingo, is known as a presumptive native from the 
islands of the Greater Antilles, with the exception of Porto Rico, and 
occurs also in Panama and in Florida. In Florida it is of recent col- 
lection, and is certainly a weed of comparatively recent introduction. 
The first record for the species in Panama ! was from waste places, and 
subsequent collections are from similar situations, so that there can 
be little doubt that the plant is an introduction in that region also, 
The five other species of the genus are each known from only one 
or at most two collections of specimens, all of which were with little 
doubt indigenous where found. The two most distinct of these come 
from Paraguay and the Galépagos Islands, respectively. Of the 
three other species, forming a very closely interrelated group, two are 
from Ecuador and one is from the Gal&pagos Islands, the latter not 
at all closely allied to the single other species of the islands. 
SYSTEMATIC TREATMENT. 
ACANTHOSPERMUM Schrank. 
Acanthospermum Schrank, Pl. Rar. Hort. Monae. pl. 53. 1819. 
Centrospermum H. B. K. Nov. Gen. & Sp. 4: 270. pl. 397. 1820. 
Orcya Vell. Fl. Flum. 344. 1825; Fl. Flum. Icon. 8: pl. 83. 1827. 
Echinodium Poit.; Cass. Dict. Sci. Nat. 59: 235, 1829, as synonym. 
Pubescent dichotomous annuals, with opposite, subentire to pinnatifid leaves and 
small, sessile or short-peduncled heads solitary in the axils and forks of the stem: 
heads heterogamous, radiate, the ray flowers 5 to 8, 1-seriate, fertile, those of the disk 
5 to 80, sterile; proper involucre of 4 to 6 elliptic to ovate, herbaceous, 1-seriate phyl- 
laries; inner phyllaries of the same number as the ray achenes and closely enveloping 
them, enlarged in fruit; receptacle small, convex, the pales membranous, concave, 
subtending the disk flowers, more or less persistent; ray corollas ligulate, small or 
medium, elliptic to ovate, emarginate or tridenticulate, the tube as long as or much 
shorter than the limb, pale yellow; disk corollas yellowish, with short cylindric tube, 
ceylindric-funnelform or campanulate throat, and 5-lobed limb; anthers barely cordate 
to cordate-sagittate at base, the appendage ovate, obtuse, somewhat inflexed; style of 
% flowers clavate, obtuse, undivided, hispidulous; fruit (achenes of the ray with their 
closely enveloping indurate phyllaries) cuneate ot oblong-fusiform, rarely trigonous- 
turbinate, weakly or strongly laterally compressed, more or less densely echinate on 
the whole surface, the angles, or rarely only at apex, with straightish or usually unci- 
nate prickles, those at the apex of fruit usually elongate; pappus none. 
Type species, A. brasilum Schrank, which is A. australe (Loefl.) Kuntze. 
' Steetz; Seem. Bot. Voy. Herald 155. 1854. 
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