X INTRODUCTION 



It gives me much pleasure to make acknowledge- 

 ment for helpful criticisms to Prof. W. A. Setchell, 

 Prof. L. H. Bailey, Prof. E. A. Harper, and Prof. 

 E. W. Hilgard. For Figs. S8a and 151 I am indebted 

 to Prof. R. H. Loughridge; for Figs. 35 and 36 to 

 Prof. L. H. Bailey; for Fig. 148a to Mr. C. K. Tuttle; 

 for Fig. 103 to Mr. N. L. Gardner; for Figs. 23a, 201 

 and 202 to Mr. L. E. Hunt; for Figs. 92, 93, and 94 

 to Prof. E. W. Hilgard; for Figs. 231 to 236 and 240 

 to 245 to Mr. Luther Burbank, and for Figs. 249, 250, 

 252 and 253 to Prof. Hugo de Vries. A few figures 

 have been redrawn from English or European sources. 

 The line drawings are, with few exceptions, the work 

 of Mr. H. N. Bagley, and the photographs, except 

 as noted above, are by Mr. B. F. White. 



BERKELEY, CAL. W. J. V. OSTERHOUT. 



January, 1905. 



