212 THE MOVEMENTS OP FLUIDS IN STEMS. 



are grown. Later in the season the bark can be most easily 

 stripped off the trees, owing to the relaxation of the tension of the 

 bark ; and if the cambium has begun to grow, the soft, easily- 

 broken-up new cells will afford the greatest facility for removing 

 the phloem and bai'k from the xylem of the stem. 



Still later the wood is soft from the new growth and the 

 absence of pressure of the bark, but in a short time as the wood 

 grows the tension increases. Lastly, the tension increases more 

 and more as the cold weather sets in after the leaves have fallen, 

 the bark contracting and exerting strong pressure on the wood, 

 and to some extent consolidating it. At the same time the 

 tension of the wood is increasing the combined effect. 



By felling in summer, although there is little reserve matter in 

 the cells, its absence is compensated for by the soft watery condi- 

 tion of the cells and the absence of tension, the wood being in a 

 much worse condition than when there is the (even at the best) 

 only comparatively small amount of reserve matters in the cells, 

 as we find existing in winter. 



We believe, therefore, that the results of the discussion held 

 last year by the Arboricultural Society, detailing as they do the 

 practical conclusions, will be found to be quite in accordance with 

 physiological fact, as determined by experiment, and are therefore 

 capable of being placed on a sound scientific, as well as on an 

 empirical basis. 



