the Alburnum of Trees. 315 
hypotheses are inconsistent with the facts that I have now the 
pleasure to communicate to you. 
Selecting parts of the stems of young trees, from which 
annual branches had sprung in the preceding year, I ascer- 
tained by injecting coloured infusions into the stems, through 
the annual shoots, that the tubes which descended from the 
latter, were, at their bases, confined to that side of the stem 
from which they sprang, and to the external annual layer of 
wood. Deep incisions were then made into the stems of 
other trees immediately beneath the bases of similar annual 
shoots, by which I am quite confident that all communication 
through the alburnous tubes, with the stem, was wholly cut 
off : yet the sap passed into the annual shoots in the succeed- 
ing spring, all of which lived, and some grew with consi- 
derable vigour. I, at the same time, selected many lateral 
branches, about three lines in diameter, in a nursery of apple 
trees, which I could easily secure to the stems of the adjoin- 
ing trees to prevent their being broken. I then made an 
incision, more than two lines deep in each, on one side, and at 
the distance of six or seven lines another incision, equally 
deep, on the opposite side ; and as I am quite certain, from 
the texture of these branches that the alburnous tubes passed 
straight through them, I am equally certain that every albur- 
nous tube was at least once intersected. Yet the sap passed 
into these branches, and their buds unfolded in the succeeding 
spring, the incisions having been made in the winter. But I 
have repeated the same experiment after the leaves have been 
full grown in the summer, and still the branches have conti- 
nued to live. 
All naturalists have agreed in stating that trees perspire 
S s 2 
