Mr. T. A. Knight on the action of 
must in this case have been derived from the mature leaves ; 
and I entertain no doubt, but that the organ] zable matter 
which occasioned their growth, was derived from the same 
source. Intersection of the bark between the mature and 
young leaves was not attended with any injurious conse- 
quences, and the sap must, therefore, have passed to the 
young leaves through the alburnum. 
Consistently with the preceding circumstances, if the ma- 
ture leaves be destroyed, or taken off, the fruit ceases to grow, 
or, if full grown, remains without richness or flavour; and 
the power of feeding fruits in winter and early spring seems 
to be confined to evergreen plants. The orange and lemon 
tree, the ivy and holly, afford familiar examples of this ; and 
where a genus of plants consists of evergreen and deciduous 
species, as that of mespilus and viburnum, the evergreen 
species alone nourish their fruit in winter and early spring. 
The probable passage of the sap from the mature to the 
young leaves and fruit, may, I think, be easily pointed out, 
though decisive proof of its course will probably never be 
adduced. Having often detached the bark from the albur- 
num of the stems of young oaks, just at the period when the 
midsummer shoots were beginning to elongate, I observed, 
as others have done, that a fluid exuded from those parts 
of the surface of the alburnum, which are called (most im- 
properly) the medullary processes, and from correspondent 
points of the bark, which resemble the medullary processes 
in organization. This fluid has been proved, by its power of 
rapidly generating an organic substance, to be the true sap of 
the tree, part of which, 1 conceive, at this period, to be pass- 
ing from the bark to join the ascending current in the albur- 
