How Trees Spend the Winter 



but untrue, that study of buds is bound to overthrow. It is the 

 behef that the woolly and silky linings of bud scales, and the 

 scales themselves, and the wax that seals up many buds are all for 

 the purpose of keeping the bud warm through the cold winter. 

 The bark, according to the same notion, is to keep the tree warm. 

 This idea is equally untenable. There is but feeble analogy 

 between a warm-blooded animal wrapped in fur, its bodily heat 

 kept up by fires within (the rapid oxidation of fats and carbo- 

 hydrates in the tissues), and the winter condition of a tree. 

 Hardy plants are of all things the most cold blooded. They are 

 defended against injuries from cold in an effective but entirely 

 different way. 



Exposure to the air and consequent loss of its moisture by 

 evaporation is the death of the cambium — that which lies under 

 the thick bark and in the tender tissues of the bud, sealed up in its 

 layers of protecting scales. 



The cells of the cambium are plump little masses of proto- 

 plasm, semi-fluid in consistency in the growing season. They 

 have plenty of room for expansion and division. Freezing 

 would rupture their walls, and this would mean disintegration and 

 death. Nature prepares the cells to be frozen without any 

 harm. The water of the protoplasm is withdrawn by osmosis 

 into the spaces between the cells. The mucilaginous substance 

 left behind is loosely enclosed by the crumpled cell wall. Thus 

 we see that a tree has about as much water in it in winter as in 

 summer. Green wood cut in winter burns slowly and oozes 

 water at the ends in the same discouraging way as it does in 

 summertime. 



A tree takes on in winter the temperature of the surrounding 

 air. In cold weather the water in buds and trunk and cambium 

 freezes solid. Ice crystals form in the intercellular spaces 

 where they have ample room, and so they do no damage 

 in their alternate freezing and thawing. The protoplasm 

 stiffens in excessive cold, but when the thermometer rises, 

 life stirs again. Motion, breathing and feeding are essential 

 to cell life. 



It is hard to believe that buds freeze solid. But cut one 

 open in a freezing cold room, and before you breathe upon it take 

 a good look with a magnifier, and you should make out the ice 

 crystals. The bark is actually frozen upon a stick of green stove 



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