140 THE GREENWOOD IREE. 



of the tree, which consists for the most part of ahnost 

 pure carbon. If you were to take a tlioroughly dry 

 piece of wood, and then drive off from it by heat tlicso 

 extraneous matters, you would find that the remainder, 

 the pure charcoal, formed the bulk of the weight, tho 

 rest being for the most part very light and gaseous. 

 Briefly put, plants are mostly carbon and water, and the 

 carbon which forms their solid part is extracted direct 

 from the air around them. 



How does it come about then that a careless world in 

 general, and more especially the happy-go-lucky race of 

 gardeners and farmers in particular, who have to deal so 

 much with plants in their practical aspect, always 

 attach so great importance to root, soil, manure, minerals, 

 and so little to the real gaseous food stuff of which their 

 crops are, in fact, composed ? Why does Hodge, who is 

 so strong on grain and guano, know absolutely nothing 

 about carbonic acid? That seems at first sight ca 

 difficult question to meet. But I think we can meet it 

 with a simple analogy. 



Oxygen is an absolute necessary of human life. Even 

 food itself is hardly so important an element in our daily 

 existence ; for Succi, Dr. Tanner, the proj)het Elijah, aud 

 other adventurous souls too numerous to mention, have 

 abundantly shown us that a man can do without food 

 altogether for forty days at a stretch, while he can't do 

 without oxygen for a single minute. Cut off his supply 

 of that life-supporting gas, choke him, or suffocate him, 

 or place him in an atmosphere of pure carbonic acid, or 

 hold his head in a bucket of water, and he dies at once. 

 Yet, except in mines or submarine tunnels, nobody ever 



