PHYSIOLOGY OF TREES. 275 



between the last and the present year's layers 

 is, however, always very distinguishable in the 

 timber; the inner side of every year's layer 

 being fuller of large tubes, and consequently 

 less solid than the outer side, which is formed 

 in the autumn, when the vigour of the growth 

 is subdued. 



It is worthy of remark, too, that where the 

 alburnum has been stripped of its bark, if small 

 portions of the cambium have been left in the 

 fissures of its surface, ^these will also swell and 

 readily unite with the collapsing- cambium in its 

 way over the wound. 



It is unnecessary to describe the other parts 

 of plants, viz. the root, leaves, stipulse, flowers, 

 and fruit, further than has been already done in 

 the directions given for the cultivation of the 

 plants especially treated of in the foregoing pages. 

 All these parts and their functions are pretty well 

 understood ; and have been far better described 

 by others than by any additional remark that 

 can be made here. Neither is it necessary that 



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