on Vegetable Physiology. 



165 



surfaces of the edges of the exposed alburnous layers ; only the 

 two developements before alluded to, \n Jig. 21., very copiously 

 produced. 



Fig. 24. represents part of the 

 stem of a tree, divested of its 

 cortical layers, and twelve layers 

 of the alburnous wood. 



This tree continues to live, 

 and appears not to be less healthy 

 than the last. In the case of 

 the exposed surfaces of albur- 

 nous layers, no vestige of sap 

 has made its appearance, except 

 from a cut that had been inad- 

 vertently made with the saw on 

 one side, to the depth of, perhaps, 

 five or six layers of wood be- 

 yond the 12: from which cut 

 a flow of sap took place, that 

 continued to run, more or less, 

 thi'ouohout the whole of last sum- 

 mer, and a little this spring, but ; 

 has latterly ceased. 



This accidental circumstance 



M 3 



