412 
THE PRINCIPLES OF BOTANY. 
remarkable for requiring a constant submersion in water for 
their well-being ; they are noticed by Professor Lindley under 
the head of Hydrates , the Hydral alliance consisting of 
several natural orders of unisexual aquatic Endogens. This 
unisexual character, however, is not universal, as the pretty 
little British plant known as Frogbit is an exception, as in 
it the flowers are bisexual. This alliance is, however, a very 
natural one, all its members grow at the bottoms of rivers, 
canals, watercourses, and ponds, elevating their foliage and 
flowers above the surface of the water in summer, and so 
performing the flowering and seeding functions. They are for 
the most part interesting plants even as represented by our 
native species, such as the frogbit, water soldier, of the pond. 
The marine sea-wrack; the Vallisneria, of New Holland, 
which, though not naturalised in our ponds, is found in 
almost every microscopist’s study ; and the Anacharis, of 
North America, which, unfortunately, though but lately in- 
troduced, is not confined to the study, but has found its way 
from thence into all our rivers and watercourses, and is at 
present doing a considerable amount of mischief. 
Of these plants we have three natural orders as under : — 
Hydrocliaridacece — Hydrocharads. 
Naiadacece — Naiads. 
Zoster acece — Sea-wracks. 
Each of these have but comparatively few genera and 
species, and these are of little or no importance in a dietetic 
or medicinal point of view, and yet they are all so full of 
interest that it seems important to give a few notes on some 
of the more prominent individuals amongst them. 
Hydrocharidac^e. 
As examples of these we would refer to such native species 
as — 
Stratiotes aldides — Water soldier. 
Hydrocharis morsus-rance — Frogbit. 
The Water soldier would seem to get its generic name 
from its sword-shaped leaves through arparog, an army, the 
truth doubtless being that on the now exploded doctrine of 
signatures the shape of the leaves pointed out that it was 
capable of curing all kinds of sword cuts. It is a com- 
paratively rare British plant, and one which some thirty 
years ago we used to meet with in Battersea Fields, but 
which modern encroachments or improvements have doubt- 
less swept away. 
