PART VIII. PICTURESQUE PLANTING. 



503 



Now though it might be shewn in some degree from vege- 

 table anatomy, and analogy from what takes place in herba- 

 ceous vegetables, I prefer deducing from the facts already stated 

 this proposition : that whatever tends to increase the wood 

 in a greater degree than what is natural to the species when in 

 its natural state, must injure the quality of timber. Pruning 

 tends to increase this in a considerable degree ; and therefore 

 it must be a pernicious practice in so far as it is used in these 

 cases *. 



6. Mr. Knight f has shewn in a very striking manner, that tim- 

 ber is produced, or rather that the alburnum or sap-wood is ren- 

 dered ligneous, by the motion of the tree during the descent of 

 the true sap. It is also sufficiently known to all who have at- 

 tended to the physiology of vegetables, and greatly confirmed 

 by some experiments recently read to the Royal Society J, that 



* In this Section I never consider pruning in regard to eradicating diseases, pre- 

 venting injuries, or increasing the natural character and tendency of trees. For 

 these purposes it is of great advantage. 



f See Phil. Trans, for 1803 — 4. Mirbell's Anatomie et Physiologie Vege- 

 tales. Tom. I. art. 6. 



% These experiments were also made by Mr. Knight. I hope they have con- 

 vinced that ingenious philosopher of an erroneous supposition in his Remarks on 

 Fruit Trees, published some years ago ; which is, that the tree produced by a 

 graft taken from one in a state of decay will live no longer than the parent plant. If 

 in these last experiments Mr. K. could reason by analogy from potatoe plants to fir 

 trees, certainly reasoning of the same nature from the propagation of decaying 

 carnations, rockets, wallflowers, &c. by layers and cuttings, to the propagation 

 of decaying fruit trees by grafts, is equally fair. We are certain that the former 

 live long after the parent plants, why not also the latter ? 



