6(3 CIRCULATION OP THE SAP. 



spring, and the return of a large portion of this matter to 

 the roots would probably be prevented :* the timber I have> 

 however, very little doubt would be much improved by 

 standing a second year, and being then felled in the autumn ; 

 but some loss would be sustained owing to the slow growth 

 of the trees in the second summer. The alburnum of other 

 trees might probably be rendered more solid and durable by 

 the same process: but the descending sap of these, being of 

 a more fluid consistence than that of the resinous tribe, would 

 escape through the decorticated space into the roots in much 

 larger quantity. 

 The increased It may be suspected that the increased solidity of the wood 

 solidity is not ;„ the fir-tree I have described was confined to the part 

 merely to the adjacent to the dtcorticated space ; but it has been long known 

 vicinity of the to gardeners, that taking off a portion of baik round the 

 space'^'^^'^ branch of a fruit-tree occasions the production of much blos- 

 som on every part of that branch in the succeeding season. 

 The .blossom rn this case probably owes its existence to a 

 stagnation of the true sap extending to the extremities of 

 the branch above the decorticated space ; and it may therefore 

 be expected that the alburnous matter of the trunk and 

 branches of a resinous tree will be rendered more solid by a. 

 ^ similar operation. 



I send you two specimens of the fir-wood I have described, 

 the one having been taken otF above, and the other below, 

 the decorticated space. The bark of (he latter kind scarcely 

 exceeded one-tenth of a line in thickness ; the cause of which 

 I propose to endeavour to explain in a future communication 

 relative to the reproduction of bark. 



* The roots of trees, though of much less diameter than their 

 trunks and branches, probably contain much more alburnum 

 and bark, because they are wholly without heart wood, and 

 extend to a much greater length than the branches ; and thence 

 it may be suspected that when fir-trees are felled, their roots, 

 contain at least as much resinous matter, in a fluid moveable 

 state, as their trunks and branches ; though not so much as is. 

 contained, in a concrete state, in the heart wood of those. 



