344 PHYTOLOGY. 



of the plant, to supply the tree above, passes directly up through this 

 part ; and, as it supplies the whole above, it must then diverge in all 

 directions. This is best seen, however, in those trees which die to the 

 heart when barked. But in others it might be supposed that the body 

 of the tree carried up its juice beyond the barked part, as in many trees, 

 the Apple, Pear, <fec. From this property the juice can be made to take 

 any direction. If a straight stem of a tree has a piece of bark removed in 

 an oblique direction, which, when carried on, runs into the spiral, the 

 sap will be conducted along the remaining bark, which, of course, is also 

 spiral (fig. 1, a b); and these spiral turns may go several times round ; but 

 this is as much as many trees can do, and more than some can bear. In 

 those whose wood does not die when barked, the spiral barking may go 

 round several times ; for we may suppose that the wood of the tree con- 

 ducts the juice, when barked in this way, as well -.as when barked all 

 round : but in those whose wood dies to the centre, the bark must 

 carry the whole juice, excepting the little bit of wood that is covered, 

 which may carry some of the juice ; but the whole or the best part must 

 go along the spiral bark. And as this in such is not sufficient if the 

 turns are many, it is necessary [in the experiment] to go at first only 

 once round the first year, then once more the second year, and so on. 

 From which it would appear that the parts acquired a facility in con- 

 ducting the juice ; or rather that the last year's bark on this spiral part 

 was so formed as to conduct the juice better than the bark at large. 



Of the Bark of Trees. — The bark of trees is that external covering 

 which may be said to have no sap in it, and hardly has any particular 

 arrangement of its parts or substance. 



This part of a tree may be divided into two kinds respecting per- 

 manency ; the first is when it is never changed, and the other where it 

 is. In the first, as this part of the tree does not grow in the same pro- 

 portion as the tree which it covers, there must be some provision in 

 nature for this ; we find in such that the bark cracks, and those cracks 

 at their bottom are filled up with new bark, probably from the sides of 

 the cracks. 



The bark appears to be one of the most essential parts of the tree — 

 it appears to be the life of the tree ; for, first, without it they cannot 

 Eve ; and, secondly, it is the immediate cause of growth, not only in 

 the part it covers, — or in other words, each part receiving its increase 

 from that part of the bark which covers it, — but the bark has a sym- 

 pathizing communication through the whole tree ; so that the tree shall 

 be variously affected, just as the bark of any particular part shall be 

 affected. 



Of the Barking of Trees. — When a tree or a branch is barked in any 



