BOOKS AND CURRENT LITERATURE 



A Desert Rubber Plant. Lloyd has published a monograph 1 

 dealing with the history, environment, morphology, reproduction, anat- 

 omy, histology, and cultivation of the Mexican rubber plant Guayule 

 (Parthenium argentatum Gray). 



This plant, discovered by J. M. Bigelow, M.D.,in 1852, was described 

 by Gray, who gives the first intimation of its economical value in the 

 Synoptical Flora, 1886, in the statement that it produces a gum or resin. 

 Its primitive use by the natives is reported, the rubber being extracted 

 by mastication and used as a ball in the Indian games. Rubber from 

 this source, extracted by a mechanical process devised by Mr. W. M. 

 A Lawrence, was placed on the market in 1904. In 1909, according to 

 Mr. Henry C. Pearson, the outlay of American capital in Mexico in con- 

 nection with this rubber industry amounted to $30,000,000. 



The total area over which Guayule is scattered is about 29,000 square 

 miles, lying mostly in the 130,000 square miles which constitute the 

 Chihuahuan Desert. The total original supply will be exhausted at the 

 present rate of consumption, in from four to six years. Data on the 

 environment are very meagre. The rainfall in 1907 is estimated at 

 about seven inches; that in 1908 somewhat over ten inches. During 

 1907 the plants were in a practically dormant condition while good growth 

 was recorded in June, 1908. The temperature (1908) ranged from 22.8° 

 for January to 100° for May and June. No measurements of soil mois- 

 ture are available. This factor controls the periods of growth of the 

 Guayule plant, growth being slight in periods of subnormal rainfall. 

 Guayule may be expected to flpwer in any month of the year if moisture 

 conditions are favorable. The relative humidity of the region is com- 

 paratively high, and this is believed to account for the greater total 

 growth than in the Arizona Desert. The rubber plant occurs normally 

 only on the coarser soils of the ridges and is seldom found on the 

 finer soils of the lowlands. Lloyd suggests that this is probably due to 

 lack of aeration in the finer soil. In the opinion of the reviewer, the 



1 Lloyd, Francis Ernest, Guayule: A Rubber Plant of the Chihuahuan Desert 

 Cam. Inst, Wash., Publ. 139, pp. viii + 213. pis. 46. 1911. 



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