50 
THE EOOD OE PLANTS, AND HOW THEY TAKE IT. 
By Dr. John A. Warder. 
A Paper read before the Pomological and Horticultural Society 
of Southern Illinois. 
Our investigations among animals disclose to us that some 
of them consume other animals for food, while others feed ex¬ 
clusively upon vegetable growth, and some, like man, are 
omnivorous. But a question of food remains to be investigated 
and answered; it is this: What is the food of plants? This 
I shall attempt to answer, though well aware that it is a 
question of no mean importance—indeed, it is the very 
foundation of all thorough understanding of scientific agri¬ 
culture and horticulture. It involves an understanding of 
vegetable physiology—a science which has received much 
attention within the past century, but which, owing to human 
imperfections, has enunciated many false propositions ; it has 
been obliged to consider, and to reconsider these, again and 
again ; each time claiming to be right, and was so believed 
until proved to be otherwise. Even now, while we advocate 
our favorite views, the honest philosopher must admit that 
he is but in his A B C of the science. The doctrines upon 
this subject that have been enunciated by Liebig are re¬ 
markable for their perspicuity, and are the most satisfactory, 
though he too has his opponents, who are not willing to admit 
the truth of the dicta of the great German agricultural 
chemist. 
Examining (as a preparatory step, before making answer) 
what plants are made of, we may find some guide in our in¬ 
vestigation. Besides small quantities of certain inorganic sub¬ 
stances, we discover certain compound bodies, which in 
chemical language are called proximate principles, such as 
cellulose, and vegetable jelly, sugar, gum, and starch, all of 
which are composed of similar elements, combined together 
in very nearly the same proportions; we also find various 
oily or fatty and waxy substances differing from the first in 
having less oxygen in their composition. Besides these we 
also find nitrogenous matters, that have a very important 
part to play in the chemical changes that the food of plants 
must undergo in its processes for the formation of the 
proximate principles just named. The two important elements 
in the food of plants, therefore, are carbon and nitrogen j the 
