496 Dale. — Origin , Development , and Morphological 
cells, containing no starch. Cells with raphides occur in both 
cortex and medulla. At this stage there is no cork. 
A tuber about three inches in diameter shows in addition 
to the buds large numbers of circular areas indicating the 
position of adventitious roots. The roots are produced most 
abundantly on the side of the tuber nearest to the point of 
attachment, although this is the side which also produces 
buds, and which, moreover, is turned towards the light as the 
tuber hangs on the stem. It should be stated that in the 
greenhouse the stem is trained horizontally on wires im- 
mediately under the glass roof. The question arises, does 
the stem grow vertically when wild, so that the roots will 
then be formed on the shaded side ? 
In a tuber of this size' the structure is the same as in 
younger stages except that a layer of cork has been developed 
externally to the cortex, and replacing the epidermis. It 
arises in the cells immediately below the epidermis. Young 
vascular bundles, and also the adventitious roots, are formed 
from the meristematic zone. 
When a large tuber is planted, one of the buds begins to 
grow rapidly and forms a strong shoot, from the base of which 
a large number of adventitious roots are produced (Figs. 3 
and 6). No use is made of the numerous well-developed 
roots already formed in the tuber. Should the first formed 
shoot meet with an accident, as happened in the case of one 
of the tubers planted in the Botanic Garden, another bud 
develops. The formation of axillary tubers on these shoots 
begins very early. 
The shoot arising from one of the tubers planted at the 
Botanic Garden was kept comparatively short, about a dozen 
or more nodes only being preserved. It was pegged down 
to the earth at intervals in order to see if it would form 
underground tubers at these points, as this is said to be 
a method of cultivation used by the Chinese to produce 
large crops of small tubers resembling potatoes 1 . At these 
Economic Products of India, p. 123 (’90). 
