CH. V, 9] 



ECONOMICS OF ROOTS 



257 



at the top. The shortening is effected by a 

 forcible expansion of the shorter cross axes, and hence a con- 

 traction of the longer vertical axes, of the cortical cells. An 

 incidental result thereof is 

 the formation, very marked 

 in some tap roots, of cross 

 wrinkles or folds, which 

 are thus explained. 



Roots, like leaves and 

 stems, exhibit abnormali- 

 ties and monstrosities, 

 though in less number and 

 diversity than other parts, 

 again no doubt because of 

 the comparatively uniform 

 conditions of life under- 

 ground. On the other 

 hand roots are especially 

 subject to an influence 

 from which leaves and 

 stems are comparatively 

 free, viz. the forcible im- 

 position upon them of 

 flattened, contorted, or 

 other peculiar shapes, of- 

 ten amusingly or gro- 

 tesquely imitative of fa- 

 miliar objects, by the rocks 

 and other impediments 



among which they grow. Such growths are often unearthed 

 and displayed as curiosities, or used in " rustic" carpentry. 



9. THE ECONOMICS, AND TREATMENT IN CULTIVATION, OF 



ROOTS 



The most important economic uses of roots depend on 

 the stores of food they contain, especially in the case of 



FIG. 181 A Ficus climbing by aid of 

 aerial roots. (From Kerner.) 



