IN EXTRA-TROPICAL COUNTRIES. 99 



mendable for places too hot iov ordinary clover, and as repre- 

 senting a large genus of plants, many of wMch may prove 

 of value for pasture. Dr. Roxburgh already gtaied that it 

 helps to form the most beautiful turf in India, and that cattle 

 are very fond of this herb. Colonel Drury informs us that it 

 is springing up on all soils and situations, supplying there the 

 place of Trifolium and Medieago. 



Dicksonia Billardierii, F. v. Mueller. {D. antartica, Labillardiere, 

 CiboUum Billardierii, Kaulf uss) . 



South-East Australia, New Zealand. This tree-fern is men- 

 tioned here, as it is the very best for distant transmission and 

 endures some frost. It attains a height of 40 feet. Impor- 

 tant also as commercial plants among fern-trees are Cyathea 

 'meAullaris, of South-East Australia and New Zealand ; Cyathea 

 dealhata, the Silvery Tree-Pern ; and G. Smithii, also of New Zea- 

 land ; because their transit in an up-grown state is not attend- 

 ed with the same diflSeulty as that of the tall AlsopAila Austra- 

 lia (which attains 60 feet), and numerous other tree-ferns, 

 about 200 species now being known ; they are also among the 

 hardiest of this noble kind of plants. Anthelminthic proper- 

 ties, which may exist in these and many other ferns, have not 

 yet been searched for. The dust-like spores should be scattered 

 through moist forest- valleys to ensure new supplies of these 

 superb forms of vegetation for the next century. 1). Bil- 

 lardierii is nowhere Antarctic. 



Digitalis purpurea, Linne. 



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

 ceedingly 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, Soutji Sea Inlands. 

 Stem prickly, as the name implies, not angular. Leaves alter- 

 nate, undivided. It ripens later than the following species, 

 a-nd requires no reeds for staking. It is propagated from 

 small tubers. This yam is of a sweetish taste, and the late 

 Dr. Seemann 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 yery 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 



