8 THE VEGETABLE WORLD. 
of fécula, whose purpose is to aid in the development of the plant 
during a certain period of its existence. 
Plants derive their principal nourishment from their roots. 
We should then naturally be led to think that the bulk of the 
Fig. 9,—Tuberons root of the Dahlia. Fig. 10.--Tubero-fibrous root of Orchis masculata, 
roots would be always in proportion to the size of the stem and 
branches of a plant. This is generally true for the same species ; 
we know, for instance, that the more numerous the branches 
of an Oak are, the more abundant are its roots; more than this, 
it is known that the strongest roots in the oak correspond with its 
strongest branches. But if we turn from one species of plant to 
another, we find, not without surprise, that the roots of the palms 
and pines bear little proportion to their height; whilst some 
plants, such as Lucerne, Bryony, and Ononis (Cammock), are pro- 
vided with enormous roots in proportion to the small dimensions 
of their stems. 
: If roots do not show in their rarifonticns the same regular and 
_ unvarying arrangement that we see in leaves and boughs, the cause 
