210 Guayule. 



The best time of the year for transplanting, as shown by the prompter 

 responses of the experiments cited in Chapter VI, is in late spring and 

 in summer, when the warmer night -temperatures aid in stimulation. The 

 differences in this regard were very noticeable and showed conclusively 

 that winter, in North Zacatecas at any rate, is unfavorable for cultural 

 operations of any kind. 



The advantage of cutting back to the region of the tap-root, in addi- 

 tion to avoiding the loss from dying back, is to be had in the behavior 

 which I have described at some length in Chapter VI, namely, the produc- 

 tion of basal shoots which root independently. These shoots will be pro- 

 duced the more frequently the nearer the tap-root the cut is made. As 

 also the guayule frequently sends out new shoots before any new roots 

 have been formed, there is less likelihood that these will exhaust the avail- 

 able moisture when the whole of the transplanted portion is covered with 

 soil. 



HARVESTING CULTIVATED GUAYULE. 



It is almost gratuitous to say anything about this topic, as up to the 

 present time the facts have not warranted cultural trials on a scale suffi- 

 cient to make available a crop of anything but limited experimental size. 

 We are justified, however, in drawing a few conclusions from the facts 

 which have been brought to light in the present paper. 



Assuming that the amount of rubber ultimately produced by guayule 

 under irrigation is sufficient to warrant its culture, it seems clear that the 

 methods of harvesting should be approximately as follows: The new 

 growths, say of two years, of plants about a meter in spread, 1 may with 

 advantage be removed by a cutting instrument, so as to leave the butt 

 undisturbed to shoot out afresh. The branches which have rooted can 

 then be removed by hand simply by breaking them away, and replanted. 

 These are usually supplied with a strong root which can be pulled up with- 

 out severe damage. In this way the cultivated stand may be increased 

 ad libitum, provided areas with sufficient water are at hand. 



CATCH CROPS. 



Immense areas of land are available in the Mesa Central of Mexico, 

 and doubtless elsewhere, where "riego temporal" is practiced. This sys- 

 tem of irrigation consists of ditches to catch the run-off, leading it to the 

 fields. The behavior of guayule would seem to justify the belief that this 

 plant could be grown for a sufficient period, say two or three years, in such 

 irrigable areas, and the expense, in part at any rate, offset by growing corn 

 or some other suitable plant, as a catch crop. The guayule, when of suffi- 

 cient size, should then be "laid by" to endure a period of drought till it 

 becomes usable, when it could be cut as suggested, and restarted. This 

 suggestion, and it is that and no more, deserves a serious trial. 



1 Assuming the conditions which have constantly been referred to in this work. 



