219 



sample with formalin in June 1905, brought in to Stanford Uni- 

 versity 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 quanti- 

 ties has proved to be a good disinfectant of the latex, but I do 

 not know how it would affect 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 Castillo, 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 pres- 

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

 of Castillo. 



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 sug- 

 gestions 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. 



CEARA RUBBER IN MEXICO. 



The only attempt to cultivate Ceara in Mexico was made a few 

 years ago by Mr. O. H. HARRISON on his Esmeralda coffee 

 plantation, some 12 miles from La Zacualpa, at an elevation of 

 ,2000 feet, on the slope of Sierra Madre. 



