Page:Philosophical Transactions - Volume 095.djvu/109

Rh the true Sap of Trees is deposited during Winter. ^5

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had given to the water the deepest colour and greatest degree of specific gravity ; but that all had afforded much extractive matter, though in every instance the quantity yielded was much less tfian I had, in all cases, found in similar infusions of winter-felled wood.

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It appears, therefore, that the reservoir of matteir deposited in the alburnum is not wholly exhausted in the succeeding spring : and hence we are able to account for the several suc- cessions of leaves and biids which trees are capable of producing when those previously protruded have. been destroyed by insects, or other causes ; and for the extremely luxuriant shoots, which often spring from the trunks of trees, whose branches have been long in a state, of decay.

I have also some reasons to believe that the matter deposited in the alburnum remains unemployed in some cases during several successive years : it does not appear probable that it can be all employed by trees which, after having been trans- planted, produce very few leaves, or by those which produce neither blossoms nor fruit. In making experiments in 1802, to ascertain the manner in which the buds of trees are repro-^ duced, I cut off in the winter all the branches of a very larg^ old pear-tree, at a small distance from the trunk ;^ and I pared off, at the same time, the whole of the lifeless external bark. The age of this tree, I have good reasons to believe, somewhat exceeded two centuries : its extremities were generally dead ; and it afforded few leaves, and no friiit ; and I had long ex- pected every successive year to terminate its existence. After being deprived of its external bark, and of all its buds, no marks of vegetation appeared in the succeeding spring, or early part of the summer: but in the beginning of July