41 



each medullary ray. The new medullary 

 rays proceeding from the new rings of pith, 

 first remarked by Dutrochet, may be easily 

 seen in oaks ; they may also be seen to 

 begin from the new layers deposited out- 

 side the ends of dead branches. 



The root has as strong a first tendency 

 downward as the stem has upward, though 

 it puzzles our philosophy to account for 

 either. The first downward tendency of 

 the root is, however, soon counteracted by 

 circumstances, such as the necessity of at- 

 mospheric aeration, the goodness of upper 

 compared with lower soils, the interven- 

 tion of rocks, chalk, &c. ; and the root is 

 found to grow horizontally, or sloping 

 upward or downward, according to the 

 inclination of the ground. I consider the 

 idea of the tap root of the oak as a vulgar 

 error. I have never seen any trace of a 

 root at any great distance from the surface 

 of the ground, nor do the stumps of oaks. 



