202 Guayule. 



HARVESTING PERIOD. 



The question of the variation in the relative rubber-content of the 

 guayule according to the time of the year is undoubtedly of more impor- 

 tance than is at present appreciated. The loss arising from this cause, 

 moreover, can not be detected by the chemical control of a factory labora- 

 tory, for the reason that the new succulent growths when dried add but 

 little to the weight of the plant, while their capacity for rubber-secretion 

 is indicated by their living volume. The "shrinkage" between field and 

 factory referred to by the manufacturer is equally inefficient as an indi- 

 cator of the loss, in a practical sense ; shrinkage consists of all kinds of loss 

 in handling and transportation from the field to the factory, an important 

 economic factor which, while including the loss under consideration, leaves 

 it undiscoverable. 



An element of uncertainty arises from the different moisture-content 

 of the shrub at various seasons. Thus, the shrinkage in weight from dry- 

 ing in field plants is from 20 to 25 per cent (exactly in my determinations 

 between 22 and 23 per cent) during drought; in irrigated plants it is as 

 high as 50 per cent. In August 1908, at the height of the growing-season, 

 the water-content ranged between 25 and 50 per cent, averaging in the 

 neighborhood of 35 to 40 per cent, as high, nearly, as in irrigated plants, 

 in which it rarely falls below 40 per cent, and is usually about 50 per cent. 

 In addition to this, the weight of the additional leaves in summer is not 

 negligible. I shall therefore venture to state with some insistence that, 

 assuming normal distribution of rainfall, the gathering of shrub during 

 summer months and for several months thereafter can mean, practically, 

 only the total loss of the rubber accretion of a whole year. The small 

 amounts of rubber undoubtedly present in the newer growths can scarcely 

 be recovered by mechanical means, while the ready breakage of the slender 

 and weak twigs of recent growth would in any event result in a loss. 



Another consideration is involved also. The germination during the 

 growing-season results in the annual crop of young seedlings, the greater 

 part of which, on account of the numbers and small size, would undoubt- 

 edly be destroyed by the peons at work collecting shrub. Aside from this, 

 the peons should be not only instructed but compelled to work carefully, 

 so as not to destroy the small plants. 



RESEEDING BARREN GROUND. 



Land from which guayule has been completely removed may, under 

 favorable conditions, be restocked by the simple operation of reseeding. 

 Whether the cost of doing this would be justified, however, is doubtful, 

 since an area of any size would require an immense amount of seed, which 

 at present it is difficult to obtain in quantities, and since the percentage 

 of germination under natural conditions would be very small. 



Whether the business view will see a sufficient monetary recompense 

 in the returns from following the procedure above recommended is not 

 the present problem. Local conditions vary too much to solve it in general 

 terms. This much, however, may be said: that the rules of operation out- 

 lined are dependable in the degree indicated, and that the disregard of 

 them, or of some equally or more efficient ones, will only lead to the prac- 

 tical extermination of the plant. 



