HOW CROPS FEED. 
INTRODUCTION. 
In his treatise entitled “ How Crops Grow,” the author 
has described in detail the Chemical Composition of Agri- 
cultural Plants, and has stated what substances are indis- 
pensable to their growth. In the same book is given an 
account of the apparatus and processes by which the plant 
takes up its food. The sources of the food of crops are, 
however, noticed there in but the briefest manner. The 
present work is exclusively occupied with the important 
and extended subject of Vegetable Nutrition, and is thua 
the complement of the first-mentioned treatise. Whatever 
information may be needed as preliminary to an under. 
standing of this book, the reader may find in “ How Cropa 
Grow.” * 
That crops grow by gathering and assimilating food is 
a conception with which all are familiar, but it is only by 
following the subject into its details that we can gain hinta 
that shall apply usefully in Agricultural Practice. 
* It has been at least the author's aim to make the first of this series of books 
prepare the way for the second, as both the first and the second are written tu 
make possible an intelligible account of the mode of action of Tillage and of 
Fertilizers, which will be the subject of a third work. 
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