22 



THE WORLD WE LIVE IX 



IT. BtowtuII 



An American elm in summer. 



tree shows that the leaves are placed so that they shade each other 

 but little, and present their flat surfaces at right angles to the 

 sun's rays. The leaves, as we shall later see, are food factories 



and do their work by 

 energy received from 

 the sun's rays. 



Roots. If we were 

 to examine the roots, 

 we would find here 

 evidences that they 

 take in water, besides 

 anchoring the tree and 

 giving it firm support. 

 Trees growing near 

 irrigating ditches or 

 sewers often fill them 

 with masses of fine 

 roots which have 

 sought out the water. 

 The smaller rootlets 

 are covered with tiny 

 absorbing organs called 

 root hairs. 



However, the tree 

 must take other ma- 

 terials than water from 

 its surroundings in 

 order to grow, for no 

 thing can live and 

 grow on water alone. 

 Our problem now be- 

 comes more difficult, and we cannot answer it completely. But 

 we do know that the green plant, taking substances from the air 

 and soil surrounding it, manufactures the material we call organic 

 food, and uses this food to make its living material. 



To discover just what a tree takes from its surroundings involves 

 the knowledge of some chemistry. Most of us have had some 



L. W. Brownell 

 The same tree, as above, during the winter. 



