Root Functions 39 



This explains how it is that we sometimes see large trees 

 with their roots sunk into the solid rock. They have sprung 

 up in that position from seeds, and as the roots have grown the 

 acid sap has gradually eaten a passage for them until they have 

 attained their present firm condition. Added to this, the root 

 exerts a mechanical force, splitting the rock in the direction of 

 pre-existing grooves, and thus helping to form a passage for 

 their growth. On the high road between Buxton and Longnor, 

 at a village called Sterndale, several large trees are close 

 to the road-side, growing through immense blocks of lime- 

 stone, which blocks have been split by the expansive force of 

 the tree. 



4. The preceding functions belong more or less to all roots; 

 there is, however, a fourth, which is only occasionally seen. In 

 some cases the root acts as a storehouse of food. 



Let us take the case of a biennial plant, such as a Turnip. 

 During the first year there are no flowers, but plenty of leaves. 

 Food materials are absorbed and converted by means of the 

 leaves into starch and other substances, which are stored up in 

 the root, which latter becomes swollen. The next year the 

 plant flowers and fruits, and this reserve of food is used up 

 during the process, so that by the end of the second year the 

 root has become shrivelled and fibrous. 



