CHAPTER XV 
PLANTS AND MEN 
“Our human souls 
Cling to the grass and water brooks.” 
—A thanase 
HE average city man gives little thought 
gk or attention to his vegetable neighbours, 
yet their continued existence is quite as vital to 
him as the air he breathes. Directly or indi- 
rectly he is utterly dependent upon them. 
Every time he sits down to a dinner table, he 
is paying an unconscious tribute to the food- 
producing abilities of plantdom. In a general 
way, plants are the world’s food producers and 
the animals are the consumers. Plants are able 
to build up living tissue from inorganic ma- 
terial. Animals must prey upon that elaborated 
structure to keep themselves alive. Plants 
separate oxygen from carbon dioxide and 
water, thereby storing up sunshine as potential 
energy. Animals reverse the process, and, re- 
combining oxygen with the plant tissue, liberate 
[215] 
