PEEFACE 



T EEGRET that pressure of other work has prevented the 

 -*- completion of this Volume within a reasonable time since 

 the publication of Volume I. Had Volume II been written 

 ten years ago, the discoveries made in the course of the last 

 decade would have given an out-of-date character to much 

 of the subject-matter. It is more especially in regard to the 

 Ferns and the extinct members of the Gymnosperms that our 

 outlook has been materially altered by recent contributions to 

 Palaeobotany. It is, howe\'er, some satisfaction to be able to 

 add that recent progress has been relatively slight in that part 

 of the subject dealt with in the first volume. 



The original intention was to complete the whole work in 

 two volumes. Soon after the second volume was begun, it 

 became evident that the remaining divisions of the plant- 

 kingdom could not be included within the compass of a single 

 volume. I decided, therefore, to take the consequences of 

 having embarked on too ambitious a plan of treatment, and 

 to preserve uniformity of proportion by reserving the seed- 

 bearing plants for a third volume. The third volume will 

 include the Pteridosperms, other than those briefly described 

 in the final chapter of the present volume, and other classes of 

 Gymnosperms. I propose also to devote such space as is 

 available within the limits of a text-book to the neglected 

 subject of the geographical distribution of plants at different 



