THE CHINESE YAM. 
179 
tion, and a convenient way of doing this is to make a sloping 
hole with an iron bar, and place the set in it, with the small 
end about two inches below the surface, the sets being six 
inches apart in the rows. The reason of their doing best 
when planted sloping, is that the new root is not then liable 
to be injured by the old one decaying. There is usually 
but one tuber to each plant, although there may be two 
or three, if anything interferes with the downward progress 
of the first root formed. If a small tuber or set be planted, 
a much larger one will be produced. If a large one be 
planted whole, one much larger still will be the result, the 
set decaying away, or becoming shrivelled as the plant is 
developed, as in the common potato. 
The serial tubers, which are globular in shape, vary in 
size from an eighth of an inch, to more than half an inch in 
diameter. These, if planted closely, will produce tubers 
from four to twelve inches in length, which, although too 
small for use, are the most suitable size for planting, to 
produce a general crop of medium-sized roots next season. 
The serial tubers are produced in great abundance on some 
of the plants, and inconspicuous flowers are also formed 
on some of them, of a greenish colour, which I have not 
observed to produce any seed. 
The plants are said to be bisexual, and if seed could 
be procured one drawback in its cultivation might be 
remedied by the selection of seedling varieties of the 
desired form. The objection referred to, is the great 
length to which the roots descend into the earth, which 
causes a considerable amount of labour in gathering the 
crop. It is singular that although the serial tubers are 
globular, the roots grown from them return to the normal 
shape, and accidental roots which are globular, when again 
planted do not produce tubers of a similar shape. No 
doubt the form of the tuber might be modified to the 
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