220 



Mr. HARRISON had considerable experience of rubber in Brazil, 

 and it struck him that Ceara rubber would be a suitable crop on 

 the highlands of Chiapas. Seeds were procured from Brazil and 

 planted on Esmeralda. The plants were left almost entirely to 

 their own device receiving very little care beyond a few sporadic 

 weedings. Compared to other Ceara trees I have seen they have 

 not developed very well, but the amount of latex is satisfactory. 

 Tapping experiments will be conducted regularly on these trees, 

 a few hundred in number. 



GUAYULE RUBBER. 

 The invention of a practical method of extracting the rubber 

 from the Guayule plant of Northern Mexico has led to over- 

 sanguine estimates of results from this new rubber industry. 

 Factories are being erected in numerous places, and the periodic 

 press reports the floating of one big company after another for the 

 purpose of exploiting the Guayule covered plains of the north of 

 Mexico, and of certain districts in the southern part of the United 

 States. 



In considering the development of the Castillo, rubber industry 

 of Central America it is necessary to pay some attention to the 

 reports on the Guayule product, especially because it has been 

 maintained by some promoters interested in the question that the 

 Guayule would supersede the production of all the other rubbers, 

 that the Guayule would lower the prices in the world's market to 

 such an extent as to render cultivation of Castillo, and Hevea an 

 impossibility, and that the Guayule would supply the entire 

 demand of the world for crude rubber. I shall here briefly discuss 

 the question. 



The much advertised Guayule rubber is obtained from 

 Parthenium argentatum A. Gray, a shrubby plant belonging to the 

 family Compositae. This plant occurs in the bush prairie forma- 

 tions of the northern part of the Mexican highlands, or more 

 specifically, in the northern districts of the states of San Luis 

 Potosi and Zacatecas, in Chihuahua, in the eastern part of Durango, 

 and in the southern districts of Coahuila. In the United States 

 the plant occurs in Texas, New Mexico and Arizona, in limited 

 areas. 



The supply of Guayule has been greatly over-estimated, princi- 

 pally because of the confusing of Guayule with another species of 

 the same genus, Parthenium incanum H. B. K., which is far more 

 abundant and grows all through the Guayule territory. This has 

 been estimated to as much as 28,000 square miles, but it must be 

 remembered that the patches of Guayule are far apart and one can 

 travel over miles in the Guayule country without seeing a single 

 specimen. The general estimates of Guayule on the acre is from 

 400 to 790 pounds, taking an average for large areas. This is 

 undoubtedly too high an average. By actual count in very favour- 

 able localities I have become convinced that even under the best 

 conditions not more than 1,500 pounds can be obtained per acre 



