410 



l^OTES AND ILLUSTEATIOITS. 



cally engaged the attention of those who have written on planting. 

 The effects of culture on other vegetables is so great as always to 

 change their appearance, and often in a considerable degree to alter 

 their nature. The common culinary vegetables, and cultivated grasses, 

 assume so different an appearance in our fields and gardens from what 

 they do in a state of wild nature, that even a botanist might easily be 

 deceived in regard to the species. The same general laws operate upon 

 the wdiole kingdom of vegetables ; and thence it is plain that the 

 effects of culture on trees, though different in degree, must be analogous 

 in their nature, -^f * * 



"The general effects of pruning I have already stated to be of a 

 corresponding nature with those of culture — that is, to increase the 

 quantity of timber produce. The particular manner in which it does 

 this is by directing the greater part of the sap, which generally spreads 

 itself in side-branches, into the principal stem. This must consequently 

 enlarge that stem in a more than ordinary degree, by increasing the 

 annual circles of the wood. Now, if the tree be in a worse soil and 

 climate than those which are natural to it, this will be of some advan- 

 tage, as the extra increase of timber will still be of a quality not 

 inferior to what would take place in its natural state ; or, in other 

 words, it will correspond with that degree of quality and quantity 

 of timber which the nature and species of the tree admit of being 

 produced. If the tree be in its natural state, the annual increase 

 of timber, occasioned by pruning, must necessarily injure its quality/ in 

 a degree corresponding with the increased quantity. If the tree be in 

 a better climate and soil than that which is natural to it, and at the 

 same time the annual increase of wood be promoted by pruning, it is 

 evident that such wood must be of a very different quality from that 

 produced in its natural state, (that is, very inferior.) 



" Now, though it might be shown in some degree from vegetable 

 anatomy, and analogy from what takes place in herbaceous 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 the timber. Pruning tends to increase this in a considerable degree ; 

 and therefore it must be a pernicious practice, in as far as it is used in 

 these cases. In this section, I have not considered pruning in regard to 

 eradicating diseases, preventing injuries, or increasing the natural cha- 

 racter and tendency of trees. For those purposes it is of great advantage. 



" Mr Knight has shown in a very striking manner, that timber is 

 produced, or rather that the alburnum or sap-wood is rendered ligneous 

 by the motion of the tree, during the descent of the true or proper sap. 



