174 



LETTERS ON TREES. 



disposition in the Yew, the Thorn, and others, — in all 

 which the development of the layer in question mani- 

 festly follows a rule widely different from any included 

 in Dr Carpenter's assumption. In that letter, I 

 adduced the facts now referred to, and others besides, 

 to shew that the ligneous fibres are none other than 

 the roots of the young plants that emanate from the 

 buds. And to what I there stated I may add this 

 other observation, that, as regards all that portion of 

 the Cambium (and of the general cellular basis) which 

 retains its cellular character, and serves to warp the 

 portion which is converted into wood or roots, it is 

 manifestly subordinate to this portion — being turned 

 aside, and in divers manners disposed of by the Hgne- 

 ous fibres or roots, as they hst. 



11. One other consideration connected with this 

 part of our subject seems to me too important to be 

 omitted. Dr Carpenter's representation of the Cam- 

 bium and buds being but ^* continuous products" and 

 a " mere extension" of the general cellular basis, is 

 scarcely in keeping with the fact, that both they and 

 their products have as definite a character, in point of 

 size and shape and form, as have the flowers and seeds. 

 Further, if this representation were correct, and if 

 nothing save extrinsic causes periodically checking 

 the extension, gives to the produce of the buds and 

 Cambium the definite character they possess, why 

 should not the leaves, for example, go on growing 



