106 SELECT PLANTS FOR INDUSTRIAL CULTURE 



Digitalis purpurea, Linne. 



Greater part of Europe. The Foxglove. A biennial and exceed- 

 ingly beautiful herb of great medicinal value, easily raised. 

 Chemical principles : digitalin, digitaletin, and three peculiar acids. 



Dioscorea aculeata, Linne.* 



The Kaawi Yam. India, Cochin-China, South Sea Islands. Stem 

 prickly, as the name implies, not angular. Leaves alternate, 

 undivided. It ripens later than the following species, and requires 

 no reeds for staking. It is propagated from small tubers. This 

 yam is of a sweetish taste, and the late Dr. Seeman regarded it as 

 one of the finest esculent roots of the globe. A variety of a 

 bluish hue, cultivated in Central America (for instance at Caracas), 

 is of very delicious taste. 



Dioscorea alata, Linne.* 



The Uvi Yam. India and South Sea Islands. The stems are four- 

 angled, and not prickly. The tubers, of which there are many 

 varieties, will attain, under favourable circumstances, a length of 

 8 feet, and the prodigious weight of one hundred pounds ! This 

 species and the preceding one are the two principal kinds cultivated 

 in tropical countries. D. alata is in culture supported by reeds. It 

 is propagated from pieces of the old root, and comes in warm climes 

 to perfection in about seven months. The tubers may be baked or 

 boiled. It is this species which has been successfully cultivated 

 in New Zealand and also in the Southern States of North America. 



Dioscorea glabra, Roxburgh.* (D. Batatas, Decaisne.) 



The Chinese Yam. From India to China. Not prickly. The root 

 is known to attain a length of 4 feet, with a circumference of 14 

 inches and a weight of about 14 Ibs. The inner portion of the 

 tuber is of snowy whiteness, of a flaky consistence, and of a delicious 

 flavour j preferred by many to potatoes, and obtained in climes too 

 hot for potato crops. The bulbilles from the axils of the leaf-stalks, 

 as in other Dioscoreas, serve as sets for planting, but the tubers 

 from them attain to full size only in the second year, the produce 

 being in proportion to the set planted. The upper end of the tubers 

 offers ready sets, but there are dormant eyes on any portion of the 

 surface of the tubers (Sir Samuel Wilson ; General Noble). First 

 grown here by the author in 1858. 



Dioscorea globosa, Roxburgh. 



India. Roxburgh states this to be the most esteemed Yam in 

 Bengal. 



