88 ACCOUNT OF SOME EXPERIMENTS ON THE 



bud, I again extracted the medulla. The leaf and bud with the lateral 

 shoot annexed (in the vine) continued to live, and did not appear to 

 suffer much inconvenience, but faded a little when the sun shone strongly 

 on them. 



I was now thoroughly satisfied that the medulla was not necessary to 

 the progression of the sap ; but I wished to see whether the wood and 

 leaf could execute their office when deprived at once of the bark and 

 medulla. With this view, I made two circular incisions through the 

 bark, above and below a leaf; and I took off the whole of the bark 

 between them 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 preceding ex- 

 periments. 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 nourishment 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 

 different fruits is evidently different, I do not consider my observations 

 such as can throw much general light on the subject. Examining 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 observa- 

 tion. Linnaeus supposes the stamina to arise from the wood. I should 

 not venture to state an opinion in opposition to his ; but I believe he has 

 not anywhere distingushed those I call the central vessels, from the com- 

 mon tubes of the wood. 



Having hitherto found that all advancing fluids appeared to pass either 



