We are working on this problem at La Zacualpa Botanical 

 Station. Herbarium specimens are secured of Castillas from 

 various parts of Central America, and seeds of different varieties 

 are being planted in the experimental plots. In due time we 

 expect to be able to throw some light on this question. Seeds of 

 our local Castilla lactiflua have been sent to various places in the 

 West Indies, to British Guiana, Gold Coast and other places in 

 West Africa, Ceylon, Java, Queensland, Philippines and Hawaii, 

 and I expect to obtain reports upon the progress and development 

 of the plant under the different conditions prevailing in these 

 different countries. 



The Geographical Distribution of Castilla. 



Castilla grows wild from 21 north latitude in Mexico south- 

 ward through Guatemala, Honduras, San Salvador, Costa Rica, 

 Nicaragua, Panama, and also in North-Western South America. 

 The area in Mexico is a belt ranging from ten to one hundred miles 

 in width and extending from the port of Tuxpan in the north to 

 the western boundary of Campeche, a distance of about 500 miles. 

 The extent of the rubber belt is also rather small in Central 

 America, where it can be said to follow the Cordilleras on both 

 sides, while in South America it grows on the western slope of the 

 Andes of Equador and Peru. 



Castilla rubber is generally known in the market as "Centrals" 

 but it derives many other names from the countries and localities 

 in which it is found growing. Thus it is called Peruvian caucho, 

 Guayaquil rubber, Barranquilla, Darien, Panama, Cartagena, 

 Honduras, Nicaragua, West Indian, Guatemala, and Mexican 

 rubber. 



The most common species is Castilla elastica Cervantes, but 

 other species such as C. mavkhamiana and C. tunu occur in different 

 regions. The question of the geographical distribution of. the 

 various representatives of the genus Castilla is not yet sufficiently 

 investigated. 



On the Isthmus of Panama the Castilla is quite common in 

 some districts. Mr. CROSS writes about its occurrence in this 

 country : 



"The Caucho tree grows not in inundated lands or marshes, 

 but in moist, undulating, or flat situations, often by the banks of 

 streamlets and on hillsides and summits where there are any loose 

 stones and a little soil. It is adapted to the hottest parts of India, 

 where the temperature does not fall much below 74 F. The tree 

 is of rapid growth, and attains a great size, and I am convinced 

 that when cultivated in India, it will answer the most sanguine 

 expectations that may have been formed concerning it. I have 

 been up the Chagres and Gatun rivers. I came out on the railway 

 about seven miles from Colon. I go back to the same place (the 

 village of Gatun) from which place by the river the India-rubber 

 forests are reached." 



