THE LIFE OF THE TREES 25 



and carbohydrates 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 pro- 

 toplasm, 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 d^ath. Nature prepares the cells to be 

 frozen without any harm. The water of the protoplasm 

 is withdrawn by osmosis into the spaces between the ceils. 

 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 summer- 

 time. 



A tree takes on in winter the temperature of the sur- 

 rounding 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 sohd. 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 





f ORES I f< 



\\J h^O 



