Variation of Water in Trees. 



115 



the season is most rapid, is coincident with the period of 

 maximum hydration of the tissues. 



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It is evident from the facts stated, that the amount of 

 water contained in trees can have no direct relation to their 

 bleeding when punctured. Indeed, it is a well-known fact 

 that the bleeding of trees, such as enables us to collect maple 

 sugar, is a purely physical process, wholly dependent upon the 

 effect of external temperature in producing variable internal 

 tension, hence in no sense connected with physiological 

 processes ; that this bleeding may occur at any time during 

 the rest period, provided the conditions of temperature are 

 favorable ; hence, that it is most pronounced when there is 

 the least water in the tissues: that during the seasons of 

 most active growth, when the plant contains most water, no 

 bleeding occurs. 



CONCLUSIONS. 



From the foregoing facts, we are justified in the conclu- 

 sions which follow: — 



(1.) The hydration of woody plants is not constant for 

 all seasons, and depends upon conditions of growth. 



(2.) The hydration reaches its maximum during the latter 

 part of May or early June, and its minimum during the 

 month of January. 



