X j.\Th'(>j>rcTn)iV 



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. 88a 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 

 ;is noted above, are by Mr. B. F. White. 



Berkeley, Cal W. J. V. OSTERHOUT. 



January, 1905. 



