The Environment. 35 



plants per hectare of 500 grams average weight, taking into account the 

 unevenness of distribution, that is, the more or less extended areas where 

 guayule does not occur. The following figures are deduced from the 

 quadrats above detailed, taking all the plants into account : 



TABLE 16. Number of plants in given areas. 



From the above it is seen that the average in long tons per hectare 

 is 4.67, per acre 1.85. 



The average weight of all the plants on the quadrats is thus seen 

 to be less than Endlich's estimate by 125 grams, or one-fourth, and as 

 these sample areas include the very best guayule land, that is, the densest 

 areas with the largest plants in relation to the density, it may be con-' 

 eluded that the present estimate is more nearly correct. In estimating 

 the average density over large areas, great difficulties are met. Endlich 

 assumed one-tenth of the area of the guayule region to be occupied by 

 the shrub at an average density of 500 to 800 kilograms per hectare. 

 This figure does not approach the indications of our data, though it 

 must be remembered that these do not take into account poor areas 

 where the shrub is very scattering or nearly absent as the Mexican 

 well expresses it "salteadito." For certain areas, e.g., one of 1,800,000 

 acres (728,744 hectares) which has been somewhat closely studied for 

 the special purpose of estimating the amount of shrub to be found there, 

 Endlich's factor was found to be very small, for if only one-hundredth 

 of its area carried guayule in the quantity of our general average, there 

 would be as much as of one-tenth of it which carried shrub of the amount 

 of his factor. We may feel sure, however, that our average applies to 

 more than one-hundredth of the total area. Whether Endlich's figure 

 applies better to the total guayule area of Mexico can not be said with 

 any certainty, but it is only fair to say that, in view of the great diffi- 

 culties involved, it is probably as near the truth as any that we might 

 venture. 







