The Cultivation of Guayule. 203 



CULTURAL OPERATIONS. 



Although it will be granted that forestal operations are of immediate 

 and great importance for the preservation of the natural stand as a source 

 of revenue for as long a period as possible, the ultimate and adequate 

 solution of the production of guayule shrub lies in its successful cultiva- 

 tion. That this is possible seems at the present not to be overstating the 

 case. The abundant and ready growth of guayule under irrigation, its 

 drought-resistant qualities, its consequent adaptability to comparativelv 

 meager irrigation, if this condition is imposed, and its ability to secrete 

 rubber, though in relatively smaller quantities per unit- volume of tissue, 

 under irrigation properly alternated with drought, are established facts. 

 It remains, therefore, to test, on a larger scale than has hitherto been 

 attempted, what may be done to establish the culture of the plant on an 

 economic basis. But in stating the positive basis for success the difficulties 

 must not be underestimated. These will be indicated in what follows, 

 and it will suffice here to point out, in a word, that the great difficulty lies 

 in the initial work of establishing the plants, which necessitates water. It 

 would be useless to attempt cultural operations without it. 



SEED. 



Should it turn out finally that the raising and the transplanting of 

 seedlings is a desirable method of procedure, the obtaining of a sufficient 

 amount of seed will be an important desideratum. At present it would 

 be necessary to collect seed from the field. This is costly and uncertain. 

 Experience has shown that the ripening of seed in the field is uneven ; much 

 of it quickly falls off, and the most satisfactory places to collect are fre- 

 quently far removed from habitations. Hand-picking is slow, but could 

 be rendered more efficient by the arrangement of a device of wire and 

 cloth, in two pieces, to be held under the shrub, from which the seed could 

 then be dislodged by light beating. It seems, however, unlikely that any 

 field method of collecting seed will be as satisfactory as its production by 

 irrigated plants, which, in the climate of North Zacatecas, will ripen seed 

 for the greater part of the year. The ripening of a large amount at one 

 time will render rapid collection easier. Some such device as suggested 

 will in any event be necessary, as the seed must be collected and submitted 

 to optimum conditions in order to get the maximum germination. It has 

 been found that the ordinary conditions of growth, even under irrigation, 

 are not efficient for this result. The advantage of growing plants under 

 irrigation is in the convenience and economy in obtaining seed, and not 

 in its superior quality. Kirkwood (1910a) found that the number of good 

 seed from irrigated plants does not exceed 17 per cent, and this is some- 

 times, but not often, surpassed in field plants. 



THE RAISING OF SEEDLINGS. 

 The small size of the seedlings and their tender character when young 

 make it necessary to handle them with considerable care. The precise 

 conditions for their successful culture have been studied by Dr. Kirkwood 

 (1910a) and by myself, and from these experiences, but more particularly 

 from my own, the following practical suggestions are made: 



