Salviniacee.] THE HIMALAYAN MOUNTAINS. 431 
- parts, both of the Old and New World, but they prevail in the greatest numbers 
in temperate climates, chiefly in ditches, and on the banks of rivers. £. palustre, 
E. sylvaticum, and E. arvense, are found in both Europe, N. America, and the two 
latter also in N. Asia. In India, one species, LE. debile, has been deseribed by 
Dr. Roxburgh as indigenous in Bengal, and has been found in Dindygul by 
Wight, in Burma by Wallich (EZ. pallens), and along the foot of the Himalayas from 
Silhet to the Deyra Doon, as well as in the Northern Doab along the banks of the 
Jumna, though some of these vary in appearance from Dr. Roxburgh’s Bengal speci- 
mens. LE. diffusum is a species described by Mr. Don from Nepal, and Which he 
informs me is identical with E. scoparium, of Wall. Cat. No. 398, and which I have 
found in the stony beds of hill streams, especially near Sahunsudhar, where, however, 
there is also another species. £. Jnglisii, nob., is a new species from Kanum, in 
Kunawur, on the northern face of the Himalayas. Equisetums were formerly recom- 
mended as medicinal agents, but they are now valued only for their mechanical pro- 
perties, as for polishing different articles, from the quantity of silex (thirteen per cent. ), 
which they contain in their cuticle. Sir D. Brewster (Lind. Nat. Ord. p. 318), observed 
these siliceous particles beautifully arranged in two lines parallel to the axes of the 
stem. From these observations, it has been concluded that the crystalline portions of 
silex and of other earths found in vegetable tissues, are integral parts of the plants 
themselves. 
, 199. MARSILEACEZ. 
The Marsileacee which were formerly united with Salviniacee, now form two orders, 
which are united into one class, Hydropterides, by Endlicher. The order, as at present 
constituted, contains Pilularia and Marsilea; the former confined to Europe, but the 
latter extending north and south, in both hot and temperate climates in the Old World, 
with a few species in N. America. The Marsileacee have their representatives also 
in the Fossil Flora, in the form of Sphenophyllum and Trizygia, the latter figured in 
the present work, Tab. 2. fig. 8. 
In India there appear to be three distinct species; J. guadrifelia, the European 
species, which is also found in New Holland, and all parts of India; M. £gyptiaca, 
which is found in the Peninsula, as well as in Egypt, and which appears to be 4. erosa, 
Willd. ; and A. coromandeliana (M. minuta of Lamarck) a species apparently peculiar 
to the most southern part of the Indian Peninsula. 
200. SALVINIACEZ. 
‘The Salviniacea, which have been usually united with Marsileacee, chiefly resemble 
aquatic Hepatice in habit; they are as extensively diffused as Marsileacee, in hot and 
temperate parts, both of the Old and New World. Salvinia natans, found in Europe 
and N. America, was found by Dr.Hamilton in Gorukpore, and obtained by myself 
from Cashmere. §S. cucullata is a new species, described by Dr. Roxburgh as being 
indigenous in Bengal. Azolla, the other genus of the order, which is extensively 
| diffused 
