WHAT A TREE IS, AND HOW IT GROWS 289 



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 as we do; it takes in oxygen 

 and gives off carbondioxid ; but the air containing the oxygen is 

 taken in through the numerous pores in the leaves called stomata, 

 and also through lehticels 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 midsummer. The autumn leaf which is 

 so beautiful has completed its work. The green starch-machinery 

 or chlorophyl, the living protoplasm in the leaf cells, has been 

 withdrawn and is safely secluded in the woody part of the tree.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 perfected, 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. 



October 



Thomas Stephens Collier 



A birdnote sounding here and there, 



A bloom, where leaves are brown and sober, 



Warm noons, and nights with frosty air, 

 And loaded wagons say, — October. 



