339 
the Ascent of the Sap in Trees. 
except a small portion round the base of the leaf. Having then 
perforated the wood, where I made each of my incisions through 
the bark, I destroyed the medulla in each place, as in the pre- 
ceding experiments. The leaf, however, continued fresh and 
vigorous; and a thin layer of new wood was formed round its 
base, as far as the bark had been suffered to remain. 
Whilst I was waiting the result of the preceding experiments, 
I made a few efforts to discover another branch of circulation, 
namely, that which takes place within the fruit, and conveys nou- 
rishment to the future offspring. My experiments were here, 
however, confined almost entirely to two species of fruit, the 
apple and the pear ; and, therefore, as the organization of diffe- 
rent fruits is evidently different, I do not consider my observa- 
tions such as can throw much general light on the subject. Ex- 
amining the fruit-stalks of the apple, the pear, the vine, and some 
other fruit-trees, I found their organization to be nearly similar 
to that of the branch from which they sprang, and to consist of 
the medulla, the central tubes, a very small portion of wood, the 
spiral tubes and those of the bark, and the two external skins. 
Tracing the progress of these in the full-grown fruits of the 
apple and pear, I found, as Linnaeus has described, that the 
medulla appeared to end in the pistilla. The central vessels 
diverged round the core, and, approaching each other again 
in the eye of the fruit, seemed to end in ten points at the base 
of the stamina, to which I believe they give existence. The 
spiral tubes, which are in all other parts appendages to these 
vessels, I could not trace beyond the commencement of the 
core ; but, as the vessels themselves extend through the whole 
fruit, it is probable that the spiral tubes may have escaped my 
observation. Linnaeus supposes the stamina to arise from the 
X x 2 
