IN EXTRA-TROPICAL COUNTRIES. 99 



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

 senting 4 a large genus of plants, many of which may prove 

 of value for pasture. Dr. Roxburgh already stated 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 Medicago. 



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

 Cibotium Billardierii, Kaulfuss). 



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 

 medullaris, of South-East Australia and New Zealand ; Cyathea 

 dealbata, the Silvery Tree-Fern ; and C. Smithii, also of New Zea- 

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

 ed with the same difficulty as that of the tall Alsophila Austra- 

 lis (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 th^^S^^^teHW^ D. Bil- 

 lardierii is nowhere Antarctic. 



Digitalis purpurea, Linne. 



Greater part of Europe. The oxgove. 

 ceedingly beautiful herb of great medicinal 

 Chemical principles : digitalin, digitaletin/ 

 acids. 



Dioscorea aculeata, Linne. 



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

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

 nate, 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. 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 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 



