Preface. v 



University of Kansas, has revised the paragraphs dealing 

 with the nature of diffusion and osmosis. Dr. S. W. Wil- 

 hston, Professor of Paleontology, University of Chicago, 

 has read the chapter on Plants of Past Ages ; S. J. Hunter, 

 Associate Professor of Comparative Zoology, University 

 of Kansas, has read those portions of Chapter VIII deal- 

 ing with the anatomy of insects; M. W. Sterling, Associate 

 Professor of Greek, University of Kansas, has revised and 

 contributed to the etymology of terms in the glossary and 

 flora; Dr. W. H. Carruth, Professor of German, Univer- 

 sity of Kansas, has revised the passages translated from 

 Sprengel. 



To all of these teachers I wish to express my grateful 

 sense of obligation for suggestions leading to the better- 

 ment of the book. 



The illustrations have been made by Miss Marguerite 

 Wise, Instructor in Botany and Zoology, University of 

 Kansas, Mr. Sidney Prentice, Miss Luella Pugh, and Miss 

 Katherine Crew. I wish to acknowledge my special in- 

 debtedness to Miss Wise, whose knowledge of the subject 

 has greatly lightened the task of preparing the illustra- 

 tions. She has made all of the wash drawings excepting 

 Fig. 192, which is by Miss Crew. Of the original line 

 drawings, Mr. Prentice made Figs. 10, 19, 21, 37, 45, 47, 

 48, 93, 180, 198, 199, 201, 202, 203, 204. The remainder 

 of the original illustrations and most of the copied figures 

 were done by Miss Wise. 



w. c. s. 



University of Kansas. 



