THE LIFE OF THE TREES 9 



tion of respiration, they may properly be called the lungs 

 of trees, for the respiration of animals differs in no es- 

 sential from that of plants. 



The bulk of the work of the leaves is accomplished before 

 midsummer. They are damaged by whipping in the 

 wind, by the ravages of fungi and insects of many kinds. 

 Soot and dust clog the stomates. Mineral deposits 

 cumber the working cells. Finally they become sere and 

 russet or "die like the dolphin," passing in all the splendor 

 of sunset skies to oblivion on the leaf mould under the 

 trees. 



TJie Groivth of a Tree 



The great chestnut tree on the hillside has cast its bur- 

 den of ripe nuts, flung down the empty burs, and given its 

 yellow leaves to the autumn winds. Now the owner has 

 cut dowTi its twin, which was too near a neighbor for the 

 wxll-being of either, and is converting it into lumber. The 

 lopped limbs have gone to the woodpile, and the boards 

 will be dressed and polished and used for the woodw^ork of 

 the new house. Here is our opportunity to see what the 

 bark of the living tree conceals — to study the anatomy of 

 the tree — to learn something of grain and wood rings and 

 knots. 



The most amazing fact is that tliis "too, too solid flesh" 

 of the tree body was all made of dirty water and carbonic- 

 acid gas. Well may we feel a kind of awe and reverence 

 for the leaves and the cambium — the builders of this 

 wooden structure we call a tree. The bark, or outer gar- 

 ment, covers the tree completely, from tip of farthest root 

 to tip of highest twig. Under the bark is the slimy, 

 colorless living layer, the cambium, which we may define as. 



