iv Preface. 



plate 4, fig. A, were made by Mr. Victor Blanco. Dr. H. van der Linde 

 obtained for me valuable material of irrigated plants from Caopas. 



Dr. Theo. Holm has afforded me the benefit of his criticism of the 

 portion of this work treating of the anatomy, and has been good enough 

 to examine inaccessible literature for me. Dr. W. E. Safford did a like 

 service regarding a few pages in the first chapter. 



To Prof. W. L. Bray I am indebted for information about the Texas 

 guayule fields, later verified by me personally ; and to my colleagues, Prof. 

 C. L. Hare and Prof. J. P. C. Southall, for assistance in making chemical 

 analyses and for mathematical formulae, respectively. 



With reference to the chapters which follow, no pretensions are 

 made with regard to completeness. The exhaustive study of a single 

 plant from all points of view might well be numbered among the labors 

 of fable. The reader is asked also to remember that the study of but 

 a single growing-period was possible. Much of the experimentation, 

 therefore, was done, as it eventually turned out, during the most un- 

 favorable season; but in the case of field experiments this was not 

 entirely a misfortune. That the theoretical bearing of many observa- 

 tions and more refined methods of making them are less attended to than 

 the matter warrants has been due to the urgent necessity of practical 

 success. With these qualifications, the work may be regarded as a 

 report on a unique opportunity, unhappily shortly terminated, to bring 

 a hitherto feral desert plant under the subjugation of culture. That suc- 

 cess may ultimately be attained is not an unreasonable nor an unwar- 

 ranted expectation, for which statement the interested reader will find 

 not a little evidence in what follows. 



Francis Ernest Lloyd. 

 Alabama Polytechnic Institute, 

 January 1910. 



