6 Addisonia 



the tubercles are rounded, with a small sharp chin below the spine- 

 duster; the small areoles are circular; the brownish spines are slender 

 and subulate, the seven to nine radial ones spreading, the central 

 one solitar}'. The flowers are central, bell-shaped, about tliree inches 

 long, pale red to pinkish white; the scales on the calyx-tube are few. 



The plant here illustrated is a small one collected by J. N. Rose at 

 CassafiFousth, Cordoba, Argentina, in 1915, which flowered in the 

 New York Botanical Garden, June 16, 1917. Its native habitat is 

 on dry hills under low bushes. 



The genus Gymnocalycium, to which the two species here illus- 

 trated belong, appeared first in the catalogue of A. Schelhase's garden 

 at Kassel in 1843, but was not formally published until 1845 when 

 Pfeifi'er referred to it three species; the following year he illustrated 

 one of these. Although Dr. Ludwig Pfeiffer was the most distin- 

 guished cactologist of his time, this genus has heretofore not been 

 accepted, nor have the species of which it is composed ever been 

 brought together even as a sub-genus. Schumann has treated the 

 species known to him in his subtribe Notocactus, but in this tribe he 

 has included other species which are not closely related to Gymnocaly- 

 cium. The genus has no close relatives in South America, being very 

 unlike Malacocarpus and Discocarpus of that region. In its flowers 

 it resembles some of the Mexican species referred to Echinocactus, 

 but is very unhke the true species of that genus. 



The species of Gymnocalycium are among the most satisfactory cacti 

 for greenhouse cultivation, for they grow well under glass and fre- 

 quently flower. They are day bloomers and the flowers last for 

 several days. The genus contains about twenty-three species, and 

 is confined to southern South America east of the Andes. BoUvia, 

 Paraguay, and Uruguay, have each two or three species, the re- 

 mainder being found in the plains and mountain valleys of Argentina. 

 Most of them are small, usually simple plants, but sometimes they 

 are cespitose, with few broad somewhat tubercled ribs. The flowers 

 are central or rarely lateral, with a more or less definite tube, bearing 

 a few scattered broad scales, and these always naked in their axils; 

 the seeds are dome-shaped and tuberculate. 



J. N. Rose. 



Explanation of Plate. Fig. 1. — Flowering plant. Fig. 2. — Portion of a 

 rib, showing an areole and a cluster of spines. 



