PREFACE V 



life in their own natural environment. At the outset there 

 may be far more botany and more reasoning power gained in 

 finding out for one's self the light relations of locust or bean 

 leaves, or in ascertaining why one pool is teeming with Spiro- 

 gyra and another with Oscillatoria, than in much reading of 

 botanical literature. 



The earlier chapters of Part I are considerably less difficult 

 than most of the later portions of the book. It is therefore 

 suggested that care should be exercised not to consume too 

 much time in covering this ground, together with the laboratory 

 work which it presupposes. Classes should rather be carried 

 along somewhat rapidly to such more difficult topics as are dis- 

 cussed in Chapters v, vui, xii, and xv, and in Part II. 



Except where acknowledgment is made in the text, the figures 

 and plates are all new or from the Foundations or Elements of 

 Botany of the senior author. Most of the illustrations of 

 Part II are original and by Dr. Davis. Special thanks for pho- 

 tographs and plates either reproduced in half tone or redrawn 

 for zinc etchings are due to F. W. Atkinson, F. Borgesen, F. E. 

 Clements, E. M. Freeman, G. L. Goodale, and Conway Mac- 

 Millan. W. M. Davis, A. E. Frye, and F. Both have kindly 

 permitted the use of a number of woodcuts and maps. 



Parts of the manuscript were read by A. T. Bell, F. E. 

 Clements, I. S. Cutter, W. F. Ganong, B. A. Harper, W. M. Hays, 

 J. C. Jensen, Miss Lillian J. MacBae, and Miss Caroline E. 

 Stringer. Proof was read by W. J. Beal, F. E. Clements, 

 W. N. Clute, I. S. Cutter, H. S. Pepoon, B. M. Stigall, and 

 Miss Eva 0. Sullivan. To all of these the authors wish to 

 express their great appreciation for kindly criticisms and most 

 helpful suggestions. J Y B 



B.M.D. 

 CAMBRIDGE, August, 1906 



