SECTION IV. 



411 



It is also sufficiently known to all who have attended to the physiology 

 of vegetables, and is greatly confirmed by some experiments recently 

 laid before the Royal Society (Philosop. Trans. 1803-1804), that the 

 solid texture of the wood greatly depends upon the quantity of sap 

 which must necessarily descend, and also on the sloivness of its descent. 

 Now, both these requisites are materially increased by side-branches, 

 which retain a large quantity of sap, and by their junction with the 

 stem occasion a contraction, and twisted direction of the vessels, which 

 obstructs the progress of the (proper) juice. That this is true in fact, 

 is well known to those accustomed to make wine from Maple or Birch 

 trees ; for in this business it is found, that those trees which have 

 fewest side-branches bleed more freely than the others, but during a 

 much shorter space of time. These hints, therefore, afford additional 

 evidence against pruning, and particularly against pruning Fir-trees, 

 which, as Mr Knight justly observes, have larger vessels than the others; 

 and therefore, when in an improved soil and climate, side-branches for 

 the purposes above mentioned are essentially necessary to them, if solid, 

 resinous, and durable timber be the object in view. 



From the foregoing remarks, I think the following conclusions may 

 be drawn respecting the management of trees. 



" First, That trees should be planted as much as possible in soils, 

 situations, and climates, analogous to tliose of their natural state; and 

 that it is chiefly in this state, or where there are some defects relative to 

 it, that pruning and culture can be exercised with advantage. 



" Secondly, That in proportion to the superiority of the soil, &c., in 

 which trees are placed over the natural soil of those trees, in the 

 same proportion pruning ought to be avoided, and thinning encouraged. 



" Thirdly, That particular regard should be had to the soil and 

 situation where either Larches or any other of the Pine tribe are 

 planted, to remain as the final crop ; for as the roots of these chiefly 

 run along the surface, and as in them the great current of the sap is 

 chiefly confined to one channel — that is, the trunk — consequently, that 

 tribe of trees is peculiarly liable to injury and change when subjected 

 to unnatural agency." — Improv. Count. Res. Vol. II. book i. p. 8. 



Nothing can be more ingenious than these speculations, or more 

 physiologically just ; and I rejoice to see that the practice of the best 

 planters is improving with the advancement of science. 



The practice of pruning, in respect to the objects to which it is 

 applied, naturally divides itself into two parts — namely, the pruning of 

 trees for ornament and for profit. In pruning for ornament, as in 

 park-wood, the less the knife is employed the better, except it be to 

 keep the tops properly balanced, or to displace some luxuriant shoot, 



