Vi PREFACE. 







The volume upon Physiological Botany (Vegetable His- 

 tology and Physiology) has been prepared by the writer's 

 colleague, Professor GOODALE. 



The Introduction to Cryptogamous Botany, both struc- 

 tural and systematic, is assigned to the writer's colleague, 

 Professor FARLOW. 



A fourth volume, a sketch of the Natural Orders of 

 Phseiiogamous Plants, and of their special Morphology, 

 Classification, Distribution, Products, etc., will be needed 

 to complete the series : this the writer may rather hope 

 than expect himself to draw up. 



ASA GRAY 



HERBARIUM OF HARVARD UNIVERSITY, 

 CAMBRIDGE. 



