n 
REVISION OF THE GENUS ACANTHOSPERMUM. 
By 8S. F. Buake. 
INTRODUCTION. 
The genus Acanthospermum, a member of the Melampodioid Heli- 
antheae, was established by Schrank in 1819 on the single species 
A. brasilum. In the following year the same species, which had 
been originally published by Loefling in 1758 as Melampodium australe, 
was again described and figured as the type of a new genus, Centro- 
spermum, in the Nova Genera et Species of Humboldt, Bonpland, and 
Kunth, and in 1825 it became the type of the genus Orcya of Velloso ; 
while the genus Echinodium of Poiteau, published as a synonym by 
Cassini in 1829, was likewise based on this species. In De Candolle’s 
Prodromus, in 1836, four species of Acanthospermum were recognized, 
divided between two sections based on the shape of the fruits. With 
the exception of two new species described from the Galapagos 
Islands by Robinson and Greenman, no other species of the genus have 
been published. In the present revision three new species from 
South America are described, bringing the total number of valid 
species in the genus to eight. 
All the species of Acanthospermum are natives of America, but with 
their spiny Xanthium-like fruits they are easily transported, and two 
have reached the Old World as widespread if scattered introductions. 
A. hispidum, found in South America from Colombia and Venezuela 
to Argentina, and native over at least a part of this region, OCCUrS as a 
weed in the southern United States as far north as New Jersey, in 
Honduras, Nicaragua, and the Lesser Antilles, and in Sénégal, 
Angola, Natal, and Hawaii. Gossweiler describes it in Angola as ‘‘a 
peculiar colonial weed appearing on waste places frequented by 
native carriers.” A. australe, likewise occurring over essentially all 
of South America, and certainly a native of that continent, has been 
collected in the Lesser Antilles, the Hawaiian Islands, and India, and 
is becoming frequent along railroads in the southern United States 
occurring sporadically as far north as Massachusetts and Oregon 
The fruits of this species, thickly covered with hooked prickles, 
383 
