4 INTRODUCTION 



has been in the water, and that the higher forms of either kingdom 

 have assumed such structural and physiological characters as enable them 

 to subsist in greater independence of aquatic surroundings than their 

 simpler progenitors. The present attempt will be to fill in certain of 

 the details into this general scheme, as applied to the vegetable kingdom, 

 and to present some connected story of how the transition may have 

 come about, as it may be seen reflected in the plants themselves, 

 whether of the present day or of the remote past. 



