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 n 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. 
