414 
THE PRINCIPLES OF BOTANY. 
has the trivial name of little water snakeweed in the United 
States, where, according to Beck, “ it occurs in still waters 
from Canada to Virginia.” 
It is, however, said not to be so common in the States as 
with us, and therefore some authors seem to consider it a 
native plant; but, as justly observed by Dr. Syme, “its 
extraordinary increase of late years is an argument in favour 
of its foreign origin, for, if it be not a new plant in our own 
rivers, how is it that it never before exhibited this remarkable 
property of rapid increase ? If it be a native, this new faculty 
has been recently imparted to it, which seems absurd.” 
During our residence at Cirencester we were constantly 
boating and botanizing on the Thames and Severn Canal, 
and we feel sure that for the first few years of our stay not 
a plant was to be seen. However, one afternoon a single 
specimen was observed, and from this, in constant visits, we 
observed its rapid spread until in three years the canal got 
so choked as to oblige its removal, when the quantity was so 
great that we were desired to investigate its properties with 
a view to making it useful as a manure, but as its solid con- 
tents were so infinitesimally small in comparison of the bulk 
it was not worth the carriage. 
At present it is in the upper parts of the River Yeo, and 
in every brook and pond near. Now, it is curious that in the 
places named, Potamogetons and other pond weeds abounded 
only a few years since, but now this interloper has driven 
out the native flora, which is accounted for by Dr. Syme on 
the following supposition — “Perhaps our sluggish streams, 
the decomposing animal and vegetable matters in the Cam- 
bridge waters, and especially the excess of lime present, may 
be favorable to its development, and form an inexhaustible 
supply of inorganic food for its nourishment and support.” 
The Zannichillia or horned-pond weed of our pools is a 
good illustration of the Naiads. This plant is curious for 
the arrangement of its flowers, as the male flower usually 
consists of a single stamen placed at the outer margin of the 
female or pistilliferous flower. 
This plant is as common to American w r aters as it is with 
us, still, as a British species, it can only he considered as 
locally abundant. 
The Zosteracece forms but a small natural order represented 
by our native Zoster a marina , the grass-wrack of our sea- coast ; 
and, as stated by Dr. Syme, “ it is found forming extensive 
submarine meadows in estuaries, the lower parts of tidal 
rivers, and muddy coasts, and likewise grows frequently in 
salt-water ditches.” 
