3 
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 lactifim 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 0 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. nmrkhamiana and’ C. twin 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 no‘t fall much below 74 0 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.” 
