X PREFACE 



used, but they are explained as they occur. It is hoped 

 that this section will be appreciated, not only by those 

 who are interested in general science, but also by teachers 

 who feel the need of a rather complete account of the 

 life-history of a gymnosperm. 



Part III is devoted to the evolution and phylogeny 

 of the cycads, the opportunity for such a study being 

 exceptionally favorable because the ancestry can be 

 traced back through geological periods, and because the 

 extinct predecessors of the living cycads are the best 

 known of all fossil plants. 



A much more extended account, technical in char- 

 acter, will be pubHshed later. 



Charles J. Chamberlain 



