14 CENTRAL AMERICAN RUBBER TREE. 



prove that rubber can be produced in cultivation, and the investment 

 of millions of dollars in Castilla culture in tropical Mexico and Cen- 

 tral America may be taken as evidence that many are convinced that 

 such production will be profitable. It is most unfortunate, however, 

 that so many of those who have been attracted by the recent revival 

 of interest in the subject have accepted the first view rather than the 

 third, and have thus needlessly jeopardized their capital by attempting 

 to grow rubber under conditions which the older experiments have 

 shown to be more or less unfavorable. 



When it is claimed that rubber culture has passed the experimental 

 stage this should be taken to mean that the agricultural production of 

 rubber has been demonstrated as possible. But from the agricultural 

 standpoint it is even more true that rubber culture has only entered 

 the experimental stage, since very little is known regarding condi- 

 tions, methods, and results. 



CASTILLA VERSUS HEVEA. 



The preceding paragraphs may serve to explain why no decision 

 has been reached on the very important question of the relative agri- 

 cultural value of the different rubber-producing trees. It has been 

 supposed thus far that the climatic and cultural requirements of the 

 Para rubber tree (Hevea) and the Central American rubber tree (Cas- 

 tilla) were quite different, but the results of the present study seem 

 to indicate that the differences, if any, have been much overestimated. 

 The comparative experiments thus far carried on in botanical gardens 

 have, at most, but a local value, and can not be accepted as final. In 

 Java, for example, both Castilla and Hevea were condemned in favor 

 of Ficus elastica (Assam rubber), but it now seems probable that the 

 continuously humid mountainous district in which the experiment 

 was tried was quite unsuited for testing the productive powers of 

 Castilla. and probably of Hevea also. 



It may be that no one rubber-producing species will attain any 

 great or exclusive preponderance, but that different climatic and soil 

 conditions can best be met by planting different trees. The wisest 

 policy in untried regions will be to make experimental plantings of 

 all of the more promising rubber trees. At present these are three 

 in number: Castilla. Hevea. and Ficus. Manihot (ceara rubber) can 

 probably be omitted from the list except for regions too dry for the 

 others. 



UNCERTAINTIES ATTENDING RUBBER CULTURE. 



Some few rubber planters have not been contented to plant any- 

 where that the rubber trees could be made to grow, or even where 

 they grew wild, but have emulated the northern farmers who planted 

 young sugar maples close by the productive parent trees. Some of 



