APRIL. 



177 



The roots of the yam, when grown to full size, are from 

 12 to 19 inches long, from 2 to 3 inches broad, and weigh 

 from 2 to 4 lbs. each, (fig. 7.) They 

 are large at the bottom end, tapering 

 gradually to the top, which is not much 

 thicker than the finger. Six roots ta- 

 ken up on the 2d November, 1855, 

 weighed 132 lbs., or 2 lbs. 4 oz. each. 

 From all that has been written upon 

 its cultivation, both in France and 

 England, but more particularly in 

 France, we gather the following hints 

 in regard to its treatment : — 



It appears to succeed best in a light, 

 loamy or sandy soil, very deep, that 

 the roots may penetrate it without any 

 obstruction. It does not appear to be 

 necessary that the earth should be very 

 rich, though no doubt it should be in 

 good condition. For field cultivation 

 it should be ploughed deep, and then 

 laid up into ridges eight or ten inches 

 high, and about eighteen inches apart; 

 but the roots should only be set out 

 in the rows, six or seven inches apart, 

 experience having proved that they 

 may be safely and economically grown 

 so close, as they are so long, and have so few side roots, that it 

 is more important to get as many of them as possible than to 

 grow them to a great size. The most profitable are those about 

 the size of carrots ; but it is all important that the ridges 

 should be high, in order to facilitate the digging. The tops 

 may be allowed to run over the ground, as is common in cul- 

 tivating the sweet potato, or they may be staked up. From 

 experiments made in France by M. Decaisne, both ways, it 

 appears there is but little difference in the crop. The roots 

 may be cut into sets an inch or two long, and planted on the 



VOL. XXII. NO. lY. 23 



7. TUBKRS OF THE DIOSCOREA. 



