106 Canadian Record of Science. 



as have come to hand, and to see how far they indicate a gen- 

 eral law. 



Theoretical considerations lead us to infer that if there is 

 any variation at all, the hydration of the structure must be 

 greatest during the period of active growth, and least during 

 the period of rest. How far this is supported by the facts, 

 will appear in the following. 



HYDRATION OF DEAD WOOD. 



Incidentally to the main question, specimens of dead wood, 

 devoid of the bark, and representing an age of four to six or 

 eight years, were collected and the moisture determined. 

 While the branches were dead, none of them were in ad- 

 vanced stages of decay, so that the contained water could 

 not be regarded as that of active decomposition, but simply 

 that which would be readily retained in the lifeless, air-dried 

 substance as exposed on the tree. The results obtained from 

 fifteen species of trees showed an extreme variation of 6.4 

 per cent., the range being from 12.9 per cent, to 19.0 per 

 cent, of water. The mean hydration obtained from these 

 determinations, was 15.1 per cent. The results appear in 

 the following table : — 



Hydration of Dead Woods. 

 Determined at 100° C. 



SPECIES. 



PER CENT. WATER. 





18.8 





19.0 





15.1 





15.9 

 13.7 





13.8 





14.0 





12.9 





13.6 





11.9 





12.9 





17.4 





15.5 





18.6 





13.5 







MEAN. 



15-1 



