34 



Guayule. 



rate of about 800 pounds per acre (1,976 pounds per hectare) , were actually 

 collected. As this was gathered under the rule that no plants less than 

 40 cm. in height or in spread were to be taken, some plants which would 

 run over 8 ounces were doubtless left, but allowing for this error probably 

 not more than 2,000 pounds to the hectare could have been taken, or at 

 most 1 ton of 2,200 pounds. On another area of 30.8 acres of the same 

 general character, but of thinner stand, 53 bales or at the rate of 344 

 pounds per acre (about 850 pounds per hectare) were gathered. 



It will thus be seen that the difficulty in estimating tonnage per 

 unit of area with small error is at best very great, and this, as already 

 said, is rendered more so by the difference in the character of the plants. 

 To judge of the truth of this, one has but to examine the various illus- 

 trations accompanying this paper. In particular, a comparison of two 

 prevalent types is shown in plate 8, namely, a slender and a spreading 

 type, but neither of extreme form. 



Table 15. Dimensions of narrow and spreading types of shrub, illustrated in plate 8. 



From the above data it is seen that, speaking broadly, the weight 

 of plants of the spreading habit is one-third to one-half greater than those 

 of the narrow type of similar height, so that a stand of the latter must 

 have a density correspondingly greater to equal in total weight a given 

 stand of the spreading type. 



As one looks over a "field" of guayule, these apparently minor dif- 

 ferences of form are not at all apparent, because of the interference of 

 other vegetation with the vision. If the occasion presents itself when 

 more accurate estimates will be demanded than at present, this condi- 

 tion will have to be taken into account. It should be further mentioned 

 that the weights given above are of freshly gathered plants. If it is 

 desired to calculate to "air-dry" shrub, the proper correction should 

 be applied, but as this is very variable, according to the season, no con- 

 stant can be given. It may, however, be as great as 22 per cent in the 

 dry season. 



The only other published calculations of this kind were made by 

 Endlich (1905, p. n 18), who, for the purpose of calculating the area of 

 guayule land necessary to support the industry, assumes the average 

 weight of the plant to be 500 grams, and the density of growth to be, 

 by weight, 500 to 800 kilograms per hectare, or from 1,000 to 1,600 



