Ill 



TREE PHYSIOLOGY 



Full in the midst of his own strength he stands, 

 Stretching his brawny arms and leafy hands, 

 His shade protects the plains, his head the hills commands. 



VIRGIL. 



ORDINARILY no one thinks of saying that 

 a tree is structurally or organically like a 

 man. In fact, we do not often worry about the 

 functions of a tree's body at all; we think of it 

 as "just growing." A man has a heart, a stomach, 

 a liver and a score of other components which are 

 always getting out of order. A tree has none of 

 these, yet it has some very definite organs which 

 perform miracles in the transformation of matter 

 quite as capably as the human variety. Like our- 

 selves, the trees draw upon substances about them 

 to build up a bodily structure of marvellous per- 

 manency and efficiency. 



A tree is a little lacking in nerves and highly 

 specialised internal organs but it has parts which 

 perform their functions. For one thing, it has a 



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