NUTRITIVE ORGANS OF PLANTS, lll 
example of this is seen in the banyan-tree of India, from the wide- 
spreading branches of which roots descend straight to the ground, so that 
a vast canopy of branches and leaves is formed, supported by numerous 


= ae 
Pea 

Fig. 73.—The Banyan-tree. 
tall columns. A banyan-tree has been described having no fewer than 
350 stems equal to large oaks, and more than 3000 smaller ones, covering 
a space sufficient to contain 7000 persons. 
Tubers and Bulbs—Some soft roots swell very much in favourable 
circumstances, storing up in their cells nourishment for the future wants 
of the plant. The swelling takes place in various forms. The turnip and 
the carrot afford instances of two of the most common forms. The tubers} 
of the potato are not properly parts of the root, but short and thick 
subterranean stems, the eyes being buds ready to send up shoots into the 
air in the spring of the following year, and the substance of the tuber 
being a provision for the nourishment of these shoots, until they become 
independent of the parent plant. Bulbs also, as those of the onion, the 
lily, and the hyacinth, are not really parts of the root, although we 
familiarly speak of such plants as bulbous-rooted, and of the potato and the 
Jerusalem artichoke as tubervus-rooted. A bulb is, in fact, a subterranean 
bud, and the true stem is the very short hard part at its base from which 
the roots spring. 
Stems.—Some plants have their stems entirely underground ; not only 
those which have extremely short stems, and are commonly described as © 
stemless, but some also in which the stem extends to a considerable length. 
A root-like stem, creeping underground, or along the surface of the 
1 Latin, ‘a swelling,’ from tumeo, to swell. 
