20 



THE MODERN PEACH PRUNER. 



solidity. We can thus readily comprehend, how a 

 shoot which has pushed forth in some portion of a 

 tree, deprived of the sun's rays, is unnaturally 

 long, and soft in its component parts. The leaves 

 of that shoot not having been exposed to the action 

 of light, the cambium has not been elaborated in 

 the texture. The sap remains much as it was 

 during its ascent ; the inner portion of the growing 

 shoot is spongy and soft, the cambium being the 

 means of hardening it, and the shoot has received 

 little or none. On the other hand, a shoot which 

 springs from that side of the branch which is fully 

 exposed to light is short, and the wood is hard, 

 well coloured, and fruitful. 



The descent of the cambium is by the innermost 

 layers of the liber, and it forms the ligneous layers 

 which cover the medullary canal, and also the 

 new vessels of the liber. 



These ligneous and cortical layers, when formed 

 from the cambium, elaborated in the upper leaves, 

 are placed above those formed by the lower leaves. 

 The ligneous layers are, however, composed from 

 the centre outwards — i.e., the newest layer is that 

 farthest from the centre. But the cortical layers 

 are formed from the circumference to the centre — 

 i.<?., the newest layer is the innermost. Each year, 

 then, a new layer of alburnum covers that formed 

 during the preceding year. When the cellular 



