18 Guayule. 



TABLE 3. Maximum and minimum, temperatures at Cedros. 



SOIL-TEMPERATURES. 



A single record of soil-temperatures extending over a period of 15 

 months was made by means of a standard pair of thermometers. The 

 instruments were buried at a depth of 10 cm. 1 below the surface of the 

 ground at station 3. The surface had a gentle slope toward NE. by E., 



50 



\ 



FIG. 2. Air-temperatures (*.) and soil-temperatures at 2 cm. depth. November 6, 1907. 



and would therefore receive neither the highest maximum nor the lowest 

 minimum insolation. The indices stood at 70 F. when the instruments 

 were buried, on December 31, 1907. They were removed April 2, 1909, 

 when the following readings were taken: maximum temperature, 94 F. ; 

 minimum temperature, 52 F. 



1 This is about the average depth at which the lateral roots of the guayule 

 are placed. 



