448 Inquiries relative to the Structure of Wood. 



the wood of the upper extremity of the branch than in 

 the lower, which was nearer to the body of the tree. 



I afterwards examined the young shoots of the current 

 year, in the same tree, as well as in several other species 

 of wood, and uniformly found that the specific gravity 

 of the young wood, that is to say, of the current year, 

 is always considerably greater than that of the same 

 species of wood when grown older. Doubtlessly, be- 

 cause it contains more sap and less air than the old 

 wood. 



In the management of experiments for determining 

 the specific gravity of wood of the current year, it is in- 

 dispensably necessary to take an account of the space 

 occupied by the pith, without which precaution we 

 shall be led to false conclusions. 



I found the specific gravity of the oak of the current 

 year to be 116,530; that of the elm 110,540. Young 

 shoots of these trees, deprived of their bark and pith, 

 descend rapidly on being thrown into water ; whilst 

 species of the same tree, more advanced in age, swim 

 on the surface, even when the wood is green, and more 

 full of sap. 



This fact is worthy the attention of persons occupied 

 in the study of vegetable physiology. 



I was next curious to examine the root of the lime 

 from which I had already had one piece of wood from 

 the trunk, and two pieces from one of its branches. 

 With this view, on the 8th of September, 1812, I caused 

 one of its roots, of about 2 inches diameter, to be 

 taken up, and cut from it a piece weighing 93.25 

 grammes, which displaced 115.8 grammes of water. Its 

 specific gravity was 80,527, and, consequently, greater 

 than that of the wood extracted from the trunk of the 



