x EDITOR'S PEEFACE. 



Nearly thirty years have elapsed since I first had the privilege of inspecting 

 those portfolios, the contents of which have, with a rare liberality, been ever 

 since placed at my disposal when desired. 



Few or no allusions are made under the Natural Orders to histological 

 characters ; to the differentiation and development of the organs ; to the 

 phenomena of fertilization ; to the functions of nutrition, circulation, and 

 respiration ; nor to the structural characters of Fossil Types, which, in the 

 case of a few Orders (chiefly Cycadece and Lycopodiacece), are of great signi- 

 ficance in reference to these and their allies. To have introduced all these 

 subjects to any useful purpose was beyond the scope of this work. A 

 companion volume devoted to them that is, one completing the Life-history 

 of the Natural Orders is the great desideratum of Botanical Science. 



It remains for the Editor and Translator to thank the Authors for their 

 confidence, both in entrusting them with the task, and in liberally per- 

 mitting the re -arrangement of the Orders according to the Editor's judgment 

 of the requirements of those for whose use the English version is made. 



Jos. D. HOOKER. 



ROYAL GARDENS, KEW : 

 December 1872. 



