404 ILLUSTRATIONS OF THE BOTANY OF [ Pistiacea. 
of Potamogeton, or Pond-weed. The last is extensively diffused throughout the world, 
the others are found both in Europe and N. America; but Nayjas in the former only. 
N. dichotoma is found in Bengal, N. spinosa, Wall. Cat. No. 5182, found by Dr. 
Hamilton at Paingti, to the east of Bengal, is very closely allied both to N. major and 
to N. marina. Caulinia indica is found as far south as Travancore ; and a species, so 
named, but different from the Peninsular plant in Rottler’s Herbarium, was found by 
Dr. Hamilton. The former may however be seen in the East-India Herbarium, Wall. Cat. 
No. 5189, but marked, apparently, by a change in the label Chara hispida, while this 
plant, or at least one of the same genus, is placed in No. 5183, and labelled Caulinia 
indica. C.? composita, Wall. Cat. No. 5184, found to the eastward of Bengal, occurs _ 
also as far north as Saharunpore, but its genus is still doubtful. 
Species of Zannichelia are also found in India, as may be seen in the East-India 
Herbarium, No. 5185, procured by Dr. Hamilton from Onaula; and also, No. 5190, 
where it is mixed up with the plant named Chara fetida, found near Pangri. Ruppia 
is also found within the limits of the Indian flora, as there are numerous specimens in 
Dr. Rottler’s Herbarium, under the name, however, of Zannichelia indica. 
Potamogeton, as mentioned, is the genus most numerous in,species, and also most 
extensive in distribution, being found in the stagnant and running waters of hot, cold, 
and temperate parts of the world. Species of Pond-weed are found in every part of 
India, and some of the same species in the northern as in the southern parts of the 
country, as Potamogeton tuberosum and P. indicum ; the latter of which, however, differs 
but little from the European P. natans ; a second species is not to be distinguished 
from P.marinum, nor another from P. rufescens (fluitans.) P.crispus is found in the 
neighbourhood of Saharunpore, and P. heterophyilus occurs in the Himalayas, in the 
vicinity of Dhargaon, on the northern face of the Choor mountain, as well as in the 
plains of India. But all the species require examination and comparison with each — 
other and with European specimens in every state. 
The several plants of this family, bland in taste and mucilaginous in nature, are not 
possessed of any active properties which would make them useful as medicinal agents ; 
but some of the Pond-weeds, especially P. tuberosum, called suwal, is much employed in 
North-western India in the process of purifying sugar. 
188. PISTIACEA. 
The small order of Pistiavee, called also Lemnacee, or the Duckweed tribe, contains 
but two genera, Pistia and Lemna: these are floating and stemless plants, and as 
simple in organization as the Fluviales, but in fructification they resemble Aroidee ; in 
fact, Pistia has the spadix of that order, but with only two flowers, and in the arrange- 
‘ment of Schott forms a tribe of that family. Lemna, which is considered as a reduced 
aroideous lant by Mr. Brown, is placed by Endlicher at the end of Fluviales ; but the 
two genera are very closely allied, and form a very natural order, which will serve to 
connect others. It is curious that the Hindoos, who have shewn themselves in many » 
things 
