73 



Handbook of Nature-Study 



the tree's diet. It is interesting to note that while the starch factories can 

 operate only in the sunlight, the leaves can digest the food and it can be 

 transported and used in the growing tissues in the dark. The leaves are 

 also an aid to the tree in breathing, but they are not especially the lungs of 

 the tree. The tree breathes in certain respects aswe do ; it takes in oxygen 



and gives off carbondi- 

 oxid; but the air con- 

 taining the oxygen is 

 taken in through the 

 numerous pores in the 

 leaves called stomata, and 

 also through lenticels in 

 the bark; so the tree 

 really breathes all over 

 its active surface. 



The tree is a rapid 

 worker and achieves most 

 of its growth and does 

 most of its work by mid- 

 summer. The autumn 

 leaf which is so beautiful 

 has completed its work. 

 The green starch-machin- 

 ery or chlorophyl, the 

 living protoplasm in the 

 leaf cells, has been with- 

 drawn and is safely se- 

 cluded in the woody part 

 of the tree. The autumn 

 leaf which glows gold or 

 red, has in it only the 

 material which the tree 

 can no longer use. It is 

 a mistake to believe that 

 the frost causes the brilliant colors of autumn foliage; they are caused 

 by the natural old age and death of the leaves and where is there to 

 be found old age and death more beautiful? When the leaf assumes its 

 bright colors, it is making ready to depart from the tree; a thin, corky layer 

 is being developed between its petiole and the twig, and when this is per- 

 fected, the leaf drops from its own weight or the touch of the slightest breeze. 

 A tree, growing in open ground, records in its shape, the direction of the 

 prevailing winds. It grows more luxuriantly on the leeward side. It 

 touches the heart of the one who loves trees to note their sturdy endurance 

 of the onslaughts of this, their most ancient enemy. 



Reference Books for Tree Study The Tree Book, Julia Rogers; Our 

 Native Trees, Harriet Keeler; Our Northern Shrubs, Harriet Keeler; The 

 Trees of the Northern States, Romayne Hough. The Trees, N. L. Britton; 

 Getting Acquainted with the Trees, J. Horace McFarland; Familiar Trees 

 and their Leaves, Schuyler Mathews; Our Trees and How to Know Them, 

 Clarence Moores Weed; A Guide to the Trees, Alice Lounsberry; The First 

 Book of Forestry, Filibert Roth; Practical Forestry, John Gifford; Trees 

 in Prose and Poetry, Stone .& Fickett; The Primers of Forestry, Pinchot. 



A stump showing rings of growth. 



