22 PHENOMENA OF PLANT-LIFE. 



upon the wood. Upon examining the tree, it was evident 

 that as it stood upon the horizontal roots which rested on 

 solid rock and had a diameter of nearly a foot ; and as they 

 had grown by the deposition of an annual layer of wood en- 

 tirely around them ; and as the heart, now several inches from 

 the rock, must once have rested on it ; and as the rock could 

 not have been depressed, therefore, the tree had been lifted 

 every year by the growing wood of the outside layer. 



Another tree of paper birch having been found growing in 

 a similar manner, one of the horizontal roots was sawed 

 through, and the centre of the heart was seen to have been 

 elevated seven inches since the tree was a seedling. 



Mr. William F. Flint, a student in the Agricultural College 

 of New Hampshire, has rendered valuable assistance in find- 

 ing specimens of trees which illustrate this principle in an 

 admirable manner. Drawings of two such examples selected 

 from a large number furnished by him are appended to this 

 paper. (Figs. 18, 19.) 



Now it is clearly demonstrated that the power of vegetable 

 growth can lift a tree, and that it must do so, whenever the 

 bed of the roots cannot be depressed. It is evident also that 

 old trees on a clay hard-pan or any other unyielding subsoil 

 must be thrown up by the process of growth. Every person 

 is familiar with the fact that large trees usually have the ap- 

 pearance of having been thus raised, and their roots are often 

 bare for a considerable distance around the trunk. 



This lifting of the tree from its bed would seem to be ad- 

 vantageous to it by tightening the roots so as to hold it firmly 

 in place, notwithstanding the possible elongation of their 

 woody fibre by the tremendous strains to which they are sub- 

 jected during violent storms. This method of securing the 

 tree in place would be still further improved by the constant 

 enlargement of the roots by the annual deposition of a layer 

 of wood, and the consequent filling of any spaces formed in 

 the soil by the movements of the roots, caused by the sway- 

 ing of the tree in the wind. 



This slight annual elevation of trees by the increase in di- 

 ameter of their horizontal roots furnishes an explanation for 

 the differences of opinion in regard to the question whether a 

 given point on the trunk of a tree is raised in the process of 



