144 



LETTERS ON TREES. 



extreme point in the ground — viz. grow dowmuards. 

 And it seems equally impossible to miss the conclusion, 

 that, as evolved ordinarily in the trunk, there is more 

 in the process of formation than meets the eye, — in 

 short (as I remarked at the close of Letter IV.), that 

 the woody fibres of the trunk — the roots of the young 

 plants that issue from the buds, do virtually though 

 not actually, potentially and in effect, though not 

 really, grow and creep downwards. 



13. And this view has the sanction of a very high 

 authority in vegetable physiology — I mean Dr Lind- 

 ley. Adverting to that disposition of the fibres which 

 I brought under your notice a little ago (§ 5, 6, and 7), 

 as seen in the Lilac^ and in Guaiacum wood, the 

 fibres in the latter crossing and interlacing," and in 

 the former turning off at every projection which 

 impedes them, just as the water of a steady but rapid 

 current would be diverted from its course by obstacles 

 in its stream," Dr Lindley observes of the disposi- 

 tion in question, that it is unintelligible upon the 

 supposition of wood being formed by a mere deposit of 

 secreted matter." And he observes further, that if 

 the new wood were a mere deposit of sach matter, 

 " the latter, as it is applied to every part of the old 

 wood, would deposit the new wood equally over the 

 whole surface of the latter, and the deviation of the 

 fibres from obstacles in their downward course would 

 scarcely occur.'' * — I am, &c. 



* Introduction to Botany, 4th ed., vol. ii. p. 193. 



