PREFATORY NOTE TO REVISED EDITION 



We have taken advantage of the opportunity presented by a 

 new issue of this volume to make certain corrections-and additions. 

 Only such changes have been made as would not break up the 

 continuity of pages. Although some corrections and additions 

 occur in the presentation of all the groups, the most numerous 

 changes will be found in the chapter on Cycadales, the group which 

 has received the most attention since the publication of the former 

 edition. The most important addition is to the Bibliography, the 

 supplementary list adding 150 titles to the 484 titles of the former 

 edition. This list will put the student in touch with the work of 

 the last seven years. 



The volume is in no sense rewritten, but it is felt that the cor- 

 rections and additions herein included will make the presentation 

 more in accord with our present knowledge of gymnosperms. 



J. M. C. 

 C. J. C. 



June 1917 



