80 



Guayule. 



in that year 3 cm. and in the following year 11 cm., a total of 14 cm. in 

 the two years. This is the largest field, plant for its age that I have seen. 

 In contrast is cited a seedling of slow growth, fully 7 years of age, entirely 

 without branches, and only 6 cm. in height. The average rate of growth 

 falls between these extremes, but nearer the lower. For the sake of brev- 

 ity, as it would serve no useful purpose to introduce large tables of fig- 

 ures, the summaries of measurements alone are given. 



The average rate of growth of 30 seedlings from 2 to 5 years old during 

 particular years is as follows: 



Table 32. 



The average amount of growth in seven seedlings for the last three 

 years, 1906-1908, is 26 mm. 



Some ten seedlings for each of the localities mentioned below were 

 measured, giving average amount of growth for two to four years, as 

 follows : 



Sierra Candelaria 22 



Station 4 (Sierra Guadaloupe) . 24 



Station 5 (Sierra Guadaloupe) . 18 



Station 2 (Sierra Zuluaga) 31 



Station 2 (Sierra Zuluaga) 40 



Station 1 (Jaguey) 30 



Cerritos de los Calzones 20 



Cedros 34 



Apizolaya 42 



Lomerio de los Zorrillos 49 



Encarnaci6n 26 



Average rate for all 30 



It will be seen that these figures, made at different times on material 

 from different localities, check each other fairly well. As said before, the 

 average rate of growth thus deduced is probably somewhat high. The 

 rate undoubtedly increases toward the fifth year, and a somewhat more 

 rapid rate is then maintained during a few years, say from the fourth to 

 the seventh, during which the total height of the plant increases at a 

 greater rate than before or after. Usually during the second or more fre- 

 quently the third year a set of branches start their growth, and with this 

 the weight increases more rapidly. What this weight may amount to in 

 four years is shown by 3 thrifty plants taken on the Lomerio de Zorrillos. 

 These made growth as follows: 



Table 33. 



