314 State in which the true Sap of Trees 



during several successive years : it does not appear probal>]o 

 that it can be all employed by trees which, aiier luivingbeeu 

 transplanted, produce very tew leaves, or bv tlio«e which 

 produce neither blossoms nor fruit. In jnaking experi- 

 ments in 1802, to ascertain the manner in which tlie buds 

 of trees are reproduced, I cut otl' in the winter ai! the 

 branches of a very large old pear-tree, at a sniali distance 

 from the trunk ; and I pared oft', at the same time, the 

 whole of the lifeless external bark. The age of tljis tree, I 

 have good reasons to believe, somewhat exceeded two cen- 

 turies : its extremities were generally dead ; and it aftbrded 

 few leaves, and no fruit ; and I had long expected every 

 successive year to terminate its existence. After being de- 

 prived 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 numerous 

 buds penetrated through the bavkin eveivpart, many leaves 

 of large size every where appeared, and in the autumn every 

 part was covered with verv vigorous shoots exceeding, in 

 the aggregate, two feet in length. The number of leaves 

 \vhich, in this case, sprang at once from the trunk and 

 hranches appeared to me greatly to exceed the whole of 

 those, which the tree had borne in the three preceding sea- 

 sons; and I cannot believe that the matter which composed 

 these buds and leaves could have been wholly prepared by 

 \h.^ feeble vegetation and scanty foliage of the preceding 

 year. 



But wlu>ther the substance which is found in the al- 

 burnum of winter-felled trees, and which disappears in part 

 in the spring and early part of the summer, be generated in 

 fjue or in several preceding years, there seem to be strong 

 grounds of probability, that this substance enters into the 

 composition of the leaf: for we have ai)uiulant reason to 

 beheve that this organ is the principal agent of assimilation j 

 and scarcely anv thing can be more contrary to every con- 

 clusion we should draw from analooical reasoning and com- 

 parison of the vegetable with the animal economy, or in it- 

 self more improbable, than that the leaf, or any other organ, 

 should sinalv prepare and assimilate !mn)ediatcly from the 

 crude aqueous sap, that matter which con">poscs itself. 



It has been contended* that the buds themselves contaia 

 the nutriment necessary for the minute unfolding leaves : 

 but trees possess ?. pr>wer to reproduce their buds, and the 

 matter necessary to form these buds must evidently be de- 

 rived from some other source : nor does it appear probable 

 that ibe young leaves very soon enter on this office ; for the 



* Thomson's Chemistry. 



expe- 



