PREFACE. 
For the last twelve years it has been the duty of the 
writer to pronounce a course of lectures annually upon 
Agricultural Chemistry and Physiology to a class in the 
Scientific School of Yale College. This volume is a result 
of studies undertaken in preparing these lectures. It is 
intended to be one of a series that shall cover the whole 
subject of the applications of Chemical and Physiological 
Science to Agriculture, and is offered to the public in the 
hope that it wili supply a deficiency that has long existed 
in English literatvre. 
The pregress of these branches of science during recent 
years has been very great. Thanks to the activity of 
numerous English, French, and especially German inves- 
tigators, Agricultural Chemistry has ceased to be the 
monopoly of speculative minds, and is well based on a 
foundation of hard work in the study of facts and first 
principles.) Vegetable Physiology has likewise made re 
') markable advances, has disencumbered itself of many 
* useless accumulations, and has achieved much that is of 
“direct bearing on the art of cultivation. 
The author has endeavored in this work to lay out a 
» ~ groundwork of facts sufficiently complete to reflect a true 
= and well-proportioned image of the nature and needs of 
- © the plant, and to serve the student of agriculture for 
= =~ thoroughly preparing himself to comprehend the whole 
= 3 
