90 



like the roots of a tree than a cone. 

 The internal cone, so ingeniously imagined 

 by De Candolle, would only exist if the 

 annual downward growth in diameter of 

 the branch ceased when it arrived at the 

 stem. Thus a branch unduly large in 

 proportion to the head of the tree will 

 form from its own deposit an excrescence 

 below it where it joins the stem ; and a 

 dead branch, or an undersized branch, 

 overgrown by the head of the tree, will 

 cause a hollow below it, from stopping the 

 downward current from the head, which 

 cannot turn sufficiently short to deposit 

 immediately below the branch. This is 

 often seen in beech trees ; and the groove 

 is sometimes prolonged the whole extent 

 of the stem. 



When a living branch is cut off a 

 vigorous tree close to the stem, new 

 growth, both of wood and of bark, is gra- 

 dually and annually deposited over the 

 end of it. This new twin growth begins 



