29 
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 
2.000 feet, on the slope of Sierra Madre. 
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 lead 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 Castilla 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 Castilla 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 obcurs 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 
