64 



Guayule. 



seeds could not get started, by maintaining a foothold till the dying off of 

 lechuguilla plants, say as the result of flowering, allowed seedlings once 

 more to take hold. 



INDUCED RETONOS. 



In order to determine the number of retonos formed after pulling up 

 (usually called "cortando") and after cutting away guayule plants, the 

 following experiments were made: 



Experiment 115. Station 2, quadrat 4. Jan. 6, 1908. 250 plants, all 

 under 40 cm. in height, were pulled up by hand, leaving in the ground only 

 such roots as were broken off by chance. Feb. 18, no growth; Mar. 29, 

 no growth; Apr. 28,5 roots produced retonos ; July 28,9 clumps of shoots 

 from as many roots started. Sept. 12, none additional. Apr. 3, 1909, 6 

 additional roots had started. 



The following measurements were made of dried material collected 

 on April 3, 1909 : 



TABLE 22. Station 2, quadrat 4. Induced retonos. 



The average amount of growth in stem -length was 8 cm. ; in diameter 

 4.4 mm. All of the new growths produced flowers, and were in normal 

 condition when examined at the close of a long drought period. One of 

 them is shown in plate 15, fig. A. 



Experiment 114. Station 2, quadrat 3, Jan. 6, 1908. Of 338 plants, 

 all but 88 small ones (i.e., 250 plants) were cut off with a "talacho" 

 from i to 5 cm. below the surface of the ground. No growth till after Mar. 

 29. Apr. 28, 1908, 40 clumps of new shoots well started, each clump of 

 2 to 6 shoots. Stems 4 to 6 cm. long, with leaves of the same length. The 

 severed roots died back about 2 cm. before the new shoots started. Depth 

 of soil at which the shoots started, 2.4 cm. July 28, 59 clumps of new 

 shoots. Sept. 1 2, none additional. Length of longest stems, 10 cm. On 

 Apr. 3, 1909, 6 clumps were removed and measured, the data from which 

 are given in table 23. 



TABLE 23. Station 2, quadrat 3. Induced retonos. 



'From a tap-root only 4.5 mm. in diameter. 



