THE VEGETATION OF MONA ISLAND 1 



N. L. BRITTON 

 New York Botanical Garden 



During the progress of the scientific survey of Porto Rico, 

 organized by the New York Academy of Sciences with the 

 aid of the American Museum of Natural History, the New 

 York Botanical Garden and Columbia University, in coopera- 

 tion with the Porto Rican Insular Government, exploration 

 has been carried out not alone on the mainland of Porto Rico 

 but on several small islands adjacent and politically a part 

 of that colony. Two of these islands lie in the Mona Passage 

 between Porto Rico and Santo Domingo, and being scientific- 

 ally almost unknown, were made points of examination in 

 February, 1914, when I visited them in company with Mr. 

 John F. Cowell, Director of the Buffalo Botanic Garden, Dr. 

 Frank E. Lutz, Assistant Curator of Invertebrate Zoology in 

 the American Museum of Natural History, and Mr. W. E. 

 Hess, Plant Propagator of the Porto Rico Agricultural Ex- 

 periment Station at Mayaguez. The trip was made in a sloop 



chartered at Mayaguez. 



Desecheo Island, lying about eighteen miles northwest of 

 Mayaguez, was first visited, and explored during two days; 

 this island is somewhat more than one square mile in area, 

 bordered by rocky coasts, rising abruptly into several hills, 

 and covered with low trees and shrubs. Its flora is essen- 

 tially identical with that of the drier parts of Porto Rico 

 and of Santo Domingo; the small tree Morisonia americana 

 and the snowy cactus (Mamillaria nivosa) have, however, not 

 yet been found on the Porto Rican mainland, although both 

 occur on the Island of Culebra east of Porto Rico, and neither 

 of them is known on Santo Domingo. The cactus Opuntia 

 haitiensis, plentiful there, is otherwise known only in His- 

 paniola, and the shrub Torrubia discolor of Hispaniola and 

 Cuba has not been found on Porto Rico. The collection made 



1 Issued May 17, 1915. 

 Ann. Mo. Bot. Gard., Vol. 2, 1915 



(33) 



