295 
qf the alburnous Vessels of Trees. 
many advantages, both as a gardener and farmer, ( parti- 
cularly in the management of fruit and forest trees,) from 
the experiments which have been the subject of my former 
memoirs, that I am confident much public benefit might be 
derived from an intimate acquaintance witli the use and office 
of the various organs of plants ; and thence feel anxious to 
adduce facts to prove that the conclusions I have drawn are 
not inconsistent with the facts stated by my great predecessors. 
It has been acknowledged, I believe, by every naturalist 
who has written on the subject, (and the fact is indeed too 
ebvious to be controverted, ) that the matter which enters into 
the composition of the radicles of germinating seeds existed 
previously in their cotyledons ; and as the radicles increase 
only in length by parts successively added to their apices, or 
points most distant from their cotyledons, it follows of ne- 
cessity that the first motion of the true sap, at this period, is 
downwards. And as no alburnous tubes exist in the radicles 
of germinating seeds during the earlier periods of their 
growth, the sap in its descent must either pass through the 
bark, or the medulla. But the medulla does not apparently 
contain any vessels calculated to carry the descending sap ; 
whilst the cortical vessels are during this period much dis- 
tended and full of moisture : and as the medulla certainly 
does not carry any fluid in stems or branches of more than 
one year old, it can scarcely be suspected that it, at any 
period, conveys the whole current of the descending sap. 
As the leaves grow, and enter on their office, cortical 
vessels, in every respect apparently similar to those which 
descended from the cotyledons, are found to descend from 
the bases of the leaves ; and there appears no reason, with 
MDCCCV'I. Q q 
