28 



is being classified by a specialist and the enzymes are carefully 

 investigated. We have tried over one hundred different chemicals 

 in regard to their disinfecting power, and we have no difficulty in 

 preserving the latex for a considerable time. By the addition of 

 formalin to the latex it can be kept for at least 27 months without 

 changing its character. This is the oldest latex I have had to deal 

 with, but I am inclined to believe that the latex can be kept 

 indefinitely. I have deposited in La Zacualpa laboratory samples 

 of latex, which are now 11 months old, and I put up a sample with 

 formalin in June 1905, brought it to Stanford University in 

 California, where I last saw it in September 1906, apparently in the 

 same condition. The 27 months old sample above referred to was 

 given me by a Mexican rubber planter, and I made from it a sample 

 of rubber, which in no way differs from that coagulated from 

 fresh latex. Salicylic acid in small quantities has proved to be a 

 good disinfectant of the latex, but I do not know how it would 

 effect vulcanization. Creosote coating and other methods of 

 mixing creosote into the latex and rubber have been tried. 



A suitable hydrometer for measuring the density of latex has 

 been devised and is used with success. 



Analyses of rubber soils have been made, and one series of 

 analyses of special interest is that of the soil on Zacualpa down to 

 a depth of 20 feet. Numerous analyses of latex of Castilla and 

 Manihot have been made, as well as of crude rubbers. The 

 chemical constituents, especially the resins, in latex from trees of 

 different ages are being compared and studied. 



Soil temperatures on the rubber plantation are taken at 

 regular intervals and comparative studies made of these with the 

 tree temperatures, and the ordinary meteorological observations 

 taken daily as to temperature, wind, light, humidity, atmospheric 

 pressure, evaporation, serve as a basis for all our studies of the 

 ecology of Castilla. 



One of the assistants made a four weeks' journey of inspection 

 to the Isthmus and Trinidad River rubber districts in May, and 

 the director of the station was dispatched, in September, on a 

 voyage round the world in order to study conditions of rubber 

 cultivation in various tropical countries as well as market condi- 

 tions in Europe and America. 



The station has been fortunate in having the confidence and 

 unlimited support of the managing director of the company, 

 Mr. O. H. Harrison, who is ready to listen to and accept all 

 suggestions based on actual scientific observation and conforming 

 to sound business principles. Many Mexican planters have re- 

 cognized the work on Zacualpa, and among others the President 

 of the Republic follows the station "with the closest interest. We 

 are often asked questions in regard to rubber culture, but as the 

 institution is a private one, we have not been able to devote time 

 to giving directions to outsiders. A series of bulletins will, how- 

 ever, be published, giving the most important results of our work. 

 Three of these bulletins are in press, but will not appear in print, 

 before the return of the director to Mexico. 



