DIMORPHIC BEANCHES OF CENTRAL AMERICAN RUBBER TREE. 33 



adventitious buds is indicated by the fact that they often appear in 

 considerable numbers along the edges of wounds, as when the bark is 

 healing over gashes made in extracting rubber. 



RELATION OF DIMOKPIIIC BRANCHES TO METHODS OF PROPAGATION. 



There is no reason to suppose that the fruit-bearing branches of 

 Castilla would take root, or that they could develop into normal 

 trees. Sections of the trunk or of the permanent branches, on the 

 other hand, take root readily, often when merely driven into the 

 ground as fence stakes. In the Soconusco district of southern Mexico 

 many instances were observed in which rubber trees were growing 

 with apparent health and vigor from plantings as fence stakes. One 

 of the largest rubber trees in the vicinity of Tapachula is said to 

 have grown from a fence stake." 



The fact that the Central American rubber tree is capable of being 

 propagated from cuttings is of practical interest in connection with 

 the great diiferences in yields of rubber from individual trees. 

 Though external conditions are undoubtedly responsible for some of 

 the ditferences, there is every reason to believe that the characteristics 

 of the individual trees will prove as important as among other culti- 

 vated plants. A system of vegetative propagation would enable such 

 differences to be utilized directly, whereas an attempt to develop im- 

 proved strains that would come true to seed might require many 

 years of breeding. The utilization of the increased vigor and fer- 

 tility of hybrids miglit also be made possible by a system of vegeta- 

 tive propagation. 



The use of large cuttings in setting out new plantations would 

 have cultural advantages in more quickly reestablishing the forest 

 conditions that are now considered desirable in rubber plantations. 

 Two of the systems of managing plantations that Avere quite popular 

 at first have been found to have serious disadvantages. The leaving 

 of the old forest to keep down the undergrowth by shade interfered 

 also with the growth of the young rubber trees. Clean culture allows 

 the trees to grow very rapidly at first, but their later development 

 ma}^ be checked if the fertile surface soil is washed away and harm- 

 ful grasses become established. The cleaning of the grassy planta- 

 tions becomes more and more expensive, and also more and more 

 harmful. The expected rate of growth of the trees is not maintained, 

 and the period of profitable production of rubber recedes into an in- 

 definite future. 



Other difficulties in rubber culture come from the refusal of the 

 latex to flow from the trees. Even when an encouraging yield is 



« Cook, O. F. The Culture of the Central American Rubber Tree, Bulletin 49, 

 Bureau of Plant Industry, U. S. Dept. of Agriculture, 1903, pi. 9. • 



58884°— Bui. 198—11 ^3 



