viii PREFACE 



study cannot safely interpret slides made by others. He is in the 

 same class with the one who claims he sees it but can't draw it ; while 

 the real trouble is not in his hand, but in his head. Studies in the 

 field bring a kind of knowledge which cannot be gained in any other 

 way; and the technical work of making slides and drawings, if prop- 

 erly done, affords a great stimulus to mental development. 



A chapter on "Alternation of Generations" has been added be- 

 cause the gymnosperms stand in such a suggestive place in the evolu- 

 tion of the sporophyte and, particularly, in the reduction of the 

 gametophyte. 



There is a single alphabetical Bibliography, numbered consecu- 

 tively. The small numerals throughout the book, both in text and 

 illustrations, refer to this Bibliography. 



It is a pleasure to acknowledge helpful advice and criticism, espe- 

 cially from Dr. A. C. NoE and Dr. Fredda D. Reed, who have read 

 the entire manuscript and have definitely improved the paleobotani- 

 cal features. Dr. John T. Buchholz read and criticized the chapter 

 on "Embryogeny of Conifers." I am indebted to Dr. E. J. Kraus for 

 suggestions in regard to the anatomy of conifers. 



Corrections and suggestions will always be welcome. 



Charles Joseph Chamberlain 



University of Chicago 

 August 1934 



