217 



with the various ingredients necessary in manufacturing different 

 articles, there is nothing to be gained in the way of preservii g 

 the " nerve" of the rubber. 



I mentioned above the disinfecting and preserving action sulphur 

 would have on the crude rubber. My series of experiments on 

 sulphurizing latex and preparing rubber from thus treated material 

 consisted of 63 different experiments, each varying from the others 

 in some more or less important respect. I made good samples of 

 rubber, and bad ones, from the sulphurized latex. In most cases 

 there was no development of bacteria in the rubber, even though 

 the samples of rubber were exposed in the culture jars to an 

 atmosphere full of spores of moulds and decaying latex was 

 poured over the rubber. Inoculation of bacteria cultures made of 

 different forms occurring in "tacky" rubber was tried, but failed 

 to develop on samples where a thorough admixture of latex and 

 sulphur has been accomplished. The preserving power of sulphur 

 mixed into the latex seems undoubted. 



I have tried many various methods of smoking the Castilla 

 rubber, and of coagulating by means of smoke. The most suc- 

 cessful one is, I believe, the following. The fumes of burning 

 sulphur were pressed into the latex for varying periods, and it 

 was found that this assisted considerably the coagulation. I then 

 mixed fumes of burning sulphur with the smoke of creosoted wood, 

 pressed this mixture through a cooling apparatus to slightly bring 

 down the temperature, and thoroughly fumigated the latex. This 

 coagulated quickly and gave a grayish rubber, perfectly transpa- 

 rent, with a high degree of tensile strength. It has not deterio- 

 rated in the six months that have passed since the experiment was 

 made. Whether this method will be incorporated in the manu- 

 facturing process on La Zacualpa depends on further experiments. 

 The present results indicate that there is a possibility in this 

 direction. 



RUBBER EXPERIMENTS. 

 Before ending this brief description of conditions on La Zacu- 

 alpa, I wish to say a few words about the experiments which 

 are being conducted at La Zacualpa Botanical Station and Rubber 

 Laboratory. This institution began its work on December 1st, 

 1905. Its purpose is the scientific investigation of the various 

 problems connected with rubber culture. In the short time of its 

 existence the station has not been able to accomplish very much 

 besides laying the foundation to a systematized study of Castilla and 

 Manihot rubbers. Considerable time was taken up in organizing 

 the work, and in equipping and arranging the laboratories. These 

 consist of a chemical laboratory, fully equipped with all necessary 

 apparatus and re-agents for analytic and experimental work ; a 

 plant physiological laboratory supplied with ordinary instuments 

 and microscopes ; a bacteriological department with all the para- 

 phernalia pertaining thereto, incubators, sterilizers, microtomes, 

 and microscopes ; a rubber experiment department with various 

 appliances ; a shop for making models and repairing instruments ; 



