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PREFACE. 



In 1907 the author of the present paper was engaged by the 

 Continental- Mexican Rubber Company and the Intercontinental Rub- 

 ber Company to organize investigations looking toward the successful 

 cultivation of a Mexican desert rubber plant, the guayule (Parthenium 

 argentatum Gray). Dr. Theodore Whittelsey and Dr. J. E. Kirkwood 

 later became identified with this undertaking, the former as chemist, 

 the latter as assistant botanist. The headquarters for the investiga- 

 tions were established at the Hacienda de Cedros, Partido de Mazapil, 

 Zacatecas, Mexico. It was not a matter for congratulation that, at the 

 close of a year, the directors found it inadvisable, for financial reasons 

 consequent on the panic of 1907, to continue the department of inves- 

 tigation. By the courtesy of the company, however, the author carried 

 on his studies for some three months beyond the termination of his 

 business relations with it, and this period, falling during the growing 

 season of 1908, brought to light many important facts. Still further 

 observations of capital importance, in part on experiments begun in 

 1907 and 1908, were made by the writer in April 1909, while represent- 

 ing the United States Rubber Company, a commission which could not 

 have been prosecuted without the kind concurrence of President C. C. 

 Thach and a number of the writer's colleagues at the Alabama Polytech- 

 nic Institute. As silence was not imposed by the United States Rubber 

 Company, it has been possible to include these observations. 



No less than hearty recognition is due also to Mr. W. H. Stay ton, 

 formerly captain, U. S. Navy, sometime president of the Continental- 

 Mexican Rubber Company, and now president of the Texas Rubber 

 Company. It is stating an open secret to say that it was through the 

 initiative and enthusiasm of this gentleman that the work of the inves- 

 tigation was undertaken and would have been continued but for cir- 

 cumstances beyond his control. Mr. Stayton has shown a liberal and 

 scientific spirit, qualities not of necessity nor at all times associated. 



Thanks are due further to Prof. J. C. Arthur and Prof. W. G. Far- 

 low for reports on various pathological matters; to Dr. M. T. Cook for 

 contributing manuscript on the galls found on guayule; to Dr. A. D. 

 Hopkins for a report on the guayule bark-borer; to Dr. L. O. Howard 

 and Dr. J. G. Sanders for the identification of certain insects; and to Prof. 

 B. L. Robinson for his courtesy in causing a photograph of the type speci- 

 men of guayule to be made. Mr. Charles S. Ridgway has rendered sub- 

 stantial aid in the preparation of certain figures. 



The drawing for figure 5 was supplied by Professor Arthur; the nega- 

 tive of plate 2, fig. B, was made by Dr. W. E. Hinds; Professor Trelease 

 furnished the illustration (fig. 4) and description of the Cedros sotol, and 

 kindly made several other determinations; the negatives of plate 3 and 



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