30 



400 to 700 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 from 

 the tjuayule patches, and these constitute less than one-tenth of 

 the total area of the territory, where the plant occurs. That my 

 estimation in this regard is upheld by others who have investigated 

 the matter and expressed an unbiased opinion is shown by the 

 following lines, translated from an article by Dr. R. Endlich, in 

 "Der Tropenpflanzer." The author says in part: — 



"The supply of the Guayule is very unevenly distributed in 

 the territory the plant occupies. In most places the plants are 

 isolated, growing sometimes in large and often in small numbers 

 among the other plants. At rare intervals small patches are found 

 where it is predominating in the chaparral flora." 



"It is very difficult to make an estimate of the average supply 

 per hectare, both on account of the uneven distribution of the 

 plant and because of the difference in size of individual specimens. 

 In favourable territory I have on several occasions counted thirty to 

 forty plants on an area of 100 square meters, which would mean a 

 total supply of 3,000 to 4,000 Guayule plants per hectare (=1,215 

 per acre). The differences in size and weight are so great that in 

 places where the plants are small and grow close together ten 

 plants have a weight of only one kilogram ( = 2 1/5 lbs.), while in 

 the best territories some of the trees weigh as much as 3 kilograms 

 each. The average weight will probably not exceed 500 grams 

 (i i/io !b.) per plant." 



" Estimates of the Guayule supply in large areas vary from 

 500 to 800 kilograms per hectare, but the distance between the 

 different places where the plants are found is often considerable, 

 and must be taken into consideration." 



The Guayule shrub is about two feet high, with knotted, 

 spreading branches and sparse, greyish leaves. The whole plant 

 contains rubber, with the exception of shoots bearing leaves and 

 flowers. Consequently the whole plant is gathered and the supply 

 is rapidly exhausted on the area, where gathering is done. Even 

 the roots are in most cases pulled up by the collector, and the 

 opportunity for re-growth is reduced to a minimum. 



The rate of growth is very slow, so that a plant 20 inches high 

 is three to four years old, while plants five years old are not more 

 than 30 inches high. Such a plant would weigh about four pounds. 

 In view of these facts it seems more than illusionary to speak of 

 growing the Guayule plant for commercial purposes. Brought 

 under domestication the plant could naturally be made to grow 

 much faster, but there are still other factors to be taken into 

 consideration. The dry country in which the Guayule plant grows, 

 has a very scanty and irregular rainfall. For an agricultural crop 

 that kind of land can hardly be expected to supply the necessary 

 requirements, and the uncertainty about the germination of the 

 seeds brings in such an element of chance, that indeed very much 



