The Cultivation of Guayule. 207 



Experiment 166 (J. E. Kirkwood). Bed prepared as above and cov- 

 ered with 4 inches of water. On the following day 250 plants 

 (seedlings) of three months or less were transplanted into this 

 bed. These plants received no more water than what was given 

 at the start, in order to test this practice in the transplanting. 

 In five days these plants appeared to be dead. 



Experiment 167 (J. E. Kirkwood). Bed prepared as before and 

 watered to saturation. Into this 15 young plants were set on 

 May 15 and immediately watered by flooding. The bed was 

 watered again on May 16. Nearly all of these lived. It resulted 

 that in 164 and 167, in which abundant watering was had at the 

 start, nearly all of the plants lived. In the others nearly all 

 failed. 



Transplanting cultivated seedlings into the natural habitat was tried, 

 but the plants were destroyed by goats. The operation is fraught with 

 much difficulty on account of the character of the ground, and would not 

 justify itself practically. 



It may properly be said that the raising of guayule seedlings, more 

 particularly during the first few weeks, is not a mere rule-of-thumb pro- 

 cedure. One has to watch them with care and learn their idiosyncrasies. 

 Later they become quite resistant and may be handled much more easily. 



The best soil for them, so far as experiments by Kirkwood (1910a) and 

 myself have shown, is the limestone soil of their natural habitat (plate 

 16). Soil which contains a good deal of humus appears unfavorable for 

 young seedlings, as, among other difficulties, damping-off is very preva- 

 lent. However, they were found to have germinated abundantly after 

 lying in such soil for seven months, and grew well, though it must not be 

 forgotten that the soil must have suffered considerable change by leaching 

 and chemical action in the interval. The action of fertilizers has not been 

 tried as yet either on seedlings or mature plants. Recent experiments 

 have, however, shown that guayule will grow well in a noncalcareous soil, 

 and respond readily to sodium nitrate. 



The presence of small stones in the soil appears on the whole to be an 

 advantage. The following experiments were done to test this point: 



Experiment 138, Jan. 24, 1908. Into three root-cages with sloping 

 glass sides three lots of seedlings of about equal size were trans- 

 planted. One (I) of these contained very finely sifted limestone 

 soil; the second (II), similar soil mixed half and half with fine 

 angular gravel of limestone; the third (III) was filled with the 

 same fine soil and coarse gravel (1 cm. ave. diam.), the gravel 

 occupying the space that it would without the soil. Feb. 22, 

 length of tap-root in (I) 50 mm. ; (II) 50 to 60 mm. ; (III) 60 to 

 120 mm. These measurements represent differences in rate of 

 growth of the tap-root, which was about the same length in all 

 at the beginning of the experiment. 



April 5, the individual measurements of the roots were as follows: 

 (I) 10, 10, 10, 10, 12.5, 14, 17 cm. Average, 11. 9 cm. 

 (II) 20, 17, 16, 13, 14, 15 cm. Average, 15.8 cm. 

 (Ill) 30, 31, 26, 2^, 26, 17, 14, 14, 20, 25 cm. Average, 22.6 cm. 



These differences were reflected in the aerial development, those of 

 III being obviously in advance of the others. 



