250 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



On the strength of the above information, Robert Cross was de- 

 tailed to Panama in 1875, by the India Office, to study the tree on the 

 spot, and to gather seeds and seedlings for distribution to the British 

 colonies possessing suitable soil and proper climatic conditions. In 

 this way the Central American rubber trees became better known 

 and were introduced into Ceylon, India, and the West Indies. Ma- 

 terials for study began to arrive at Kew, and on December 3, 1885, 

 Sir Joseph Dalton Hooker read before the Linnean Society a memoir 

 " On the Castilloa elastica Cervantes and some allied rubber-yield- 

 ing plants," in which he admitted the probable existence of more 

 than one species of Castilla and insisted on the necessity of a more 

 accurate study of the genus. In this paper, however, he reduced 

 C. costaricana Liebm., cited erroneously as U C. eosta-ricensis" to the 

 rank of a synonym of C. elastica, a step that must be considered a 

 retrograde one and justified only by the evident lack of authentic 

 information. Although short descriptions and good illustrations 

 were given, Hooker made no attempt toward establishing any new 

 species. 



In recent years, the now adult trees introduced everywhere in the 

 Tropical Zone in botanical gardens and at agricultural stations have 

 been widely experimented upon with varying results and a large 

 amount of capital has been invested in plantations, most of which 

 have failed thus far to justify the oversanguine expectations of the 

 investors. The lack of uniformity in the behavior of the tree under 

 cultural conditions, has awakened a suspicion of specific diversity, 

 but the absence of adequate specimens in the botanical collections 

 has defeated the efforts of most investigators to reach a conclusion as 

 to whether Castilla is or is not a monotypic genus. 



In 1900, however, Mr. Hemsley advanced toward the solution of 

 the question by publishing his C. tunu, unfortunately founded upon 

 specifically heterogeneous materials, to which he added the follow- 

 ing year G. australis, growing at the southernmost limit of the generic 

 area. 



But the real investigation of the Central American species of Cas- 

 tilla began in 1902, when Mr. O. F. Cook went to southern Mexico 

 expressly to further our knowledge of rubber-producing plants and 

 the possibilities of their systematic cultivation. In 1903 he pub- 

 lished in a memoir full of original views and of useful hints the 

 results of his first researches, and these were actively continued dur- 

 ing the subsequent years and extended to Guatemala and Costa 

 Rica. In the course of his travels, Mr. Cook lost no opportunity to 

 secure complete material, preserved in alcohol, so as to make possible 

 a thorough study of the anatomical and structural features of the 

 several parts. In 1905, he was able to publish a good synopsis of the 

 characters of no less than seven species, of which four were new and 



