. Handbook of nature-study for teachers and parents, based on the Cornell nature-study leaflets. Nature study. 73° Handbook of Nature-Study the tree's diet. It is interesting to note that while the stareh 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 ofE carbondi- oxid; but the air con- taining the oxygen is taken in t
. Handbook of nature-study for teachers and parents, based on the Cornell nature-study leaflets. Nature study. 73° Handbook of Nature-Study the tree's diet. It is interesting to note that while the stareh 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 ofE 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 briUiant 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 liixuriantly 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
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