164 VEGETABLE ORGANOGRAPHY. 



the middle of several trees. Two Meraoires by Fouge- 

 roux de Bondaroy, inserted among those of the Aca- 

 demie de Paris for 1777, may be particularly consulted 

 upon this subject. 



When any accidental cause, as the hand of man, the 

 teeth of animals, or simply a morbid change, hollows 

 out a cavity in the alburnum, the orifice of which is suf- 

 ficiently narrow to be covered over by the subsequent 

 woody layers, the cavity is preserved entire, as well as 

 any objects shut up in it. I have seen, for example, in 

 the middle of a large piece of Oak, which appeared per- 

 fectly sound, a cavity partly filled with nuts and acorns, 

 which had probably been carried there by dormice or 

 squirrels, before it was covered over by new woody 

 layers. In the same manner bones, stones, &c., are 

 found in similar cavities. 



When a nail is driven into a tree, so as to reach the 

 alburnum, it remains fixed, and, by degrees, the new 

 woody layers which are formed around it surround its 

 base, so that it appears as if it had been driven into 

 them ; sooner or later it is entirely covered over : it is 

 thus that we find nails and other instruments, or the 

 horns of stags, infixed, or completely sunk, in the 

 wood of Exogenous trees. It is by the same process 

 that the base of the Mistletoe appears each year to sink 

 into the tree, because the woody layers rise up around 

 it. We shall find a more general application of these 

 principles when we come to the Formation of the 

 Branches. We shall see by-and-by, that phenomena 

 diametrically opposite to those we have been describing, 

 take place in the cortical layers. 



As a consequence of the preceding facts, and of the 

 mode of nutrition of Exogens, it happens that if the 

 stem of a tree of this class be surrounded by a cord or 

 wire, the trunk, by growing, becomes contracted here ; 



