PHYSIOLOGY OF VEGETABLES. 119 



3. It lias been stated that grapes came to maturity 

 much earlier, were larger, asiu setter flavoured when 

 a small circle of bark, one or two eighths of an inch 

 wide, was removed from around the alburnum of the 

 fruitful branches, while the fruit was in its young state. 

 Dr. Bigelow mentions that this method is annually 

 practised in the vicinity of Boston, by different indi- 

 viduals, with the best success. See Smith's Botany, 

 page 59. According to Mr. Knight's theory, the ex- 

 planation is obvious, The sap continues to ascend 

 with freedom, but being interrupted in its descent, and 

 confined to the branches above the incision, a geater 

 quantity of it goes to nourish the fruit. 



4. Du Hamel, by many experiments, proved the 

 wood to be deposited from the innermost part of the 

 bark or Liber. He introduced plates of tinfoil under the 

 bark of growing trees, arid after some years, on cut- 

 ting them across, he found the layers of new wood, 

 equal to the number of years, on the outside of the tin. 



Observation. Linnaeus had a peculiar notion that the new layers 

 were secreted annually from the pith, and added internally to the 

 former ones. 



5. It has been mentioned, that at a particular sea- 

 son, trees may be stripped of their bark without inju- 

 ry, a new bark being speedily formed. This was 

 thought to go against the theory, but if it be true, 

 as I have suggested, page 116, that the rudiment 

 of the new bark is formed before the old bark is re- 

 moved, and is not removed with it, but remains on the 

 wood, it accords perfectly with it. 



8. Of the power which elevates the Sap. 



The manner in which the sap is propelled through 

 the several tubes, and elevated to the top of the tallest 

 tree, seems not to be well understood. 



Whatever may be the action which propels the fluids, 

 it must possess great power, for the mass of fluid in a 

 large tree, which is not only supported by it, but mov- 



