IV PREFACE. 



The preparation of the volume upon Physiological 

 Botany (Vegetable Histology and Physiology) is assigned 

 to the author's colleague, Professor GOODALE. 



The Introduction to Cryptogamous Botany, both structu- 

 ral and systematic, is assigned to his colleague, Professor 

 FABLOW. 



A fourth volume, a sketch of the Natural Orders of 

 Phaenogamous Plants, and of their special Morphology, 

 Classification, Distribution, Products, &c., will be needed 

 to complete the series : this the present author may 

 rather hope than expect himself to draw up. 



ASA GRAY. 



HERBARIUM OF HARVARD UNIVERSITY, 

 CAMBRIDGE April 10, 1879. 



into sentences or appended to them, are references to the numbered para- 

 graphs in which the topic is treated or the term explained. 



