8 
found ; but this is independent altogether of that condition, 
and actually grows as it travels slowly down the stream, after 
» 
being cut. The specific gravity of it is so nearly that of 
water, that it is more disposed to sink than float, and the cut 
masses may be seen under water, either on or near the 
bottom, rolling over and over like woolpacks, clinging to 
. every thing they meet with, and accumulating in great 
quantities at locks and bridges (hugging the piers of the 
latter), and grounding in shoal water. Its mode of growth 
may be best seen in still and narrow waters, (such as the 
stream above the mills at Cambridge), where it seems to 
spring first from the two sides and bottom, meeting at length 
in the middle, and completely filling up the watercourse, as 
I have seen-in some cases, almost to the exclusion of the 
water. Except in very quiet places it is not likely to be 
found in flower. I have, however, found it flowering in great 
profusion just below Ely ; but as the plant is diecious, (i.e. 
producing male and female flowers on separate individuals), 
there is no fear, as I have before remarked, of its producing 
seeds in this country, all the specimens hitherto found being 
of one sex only, 
Although there is little doubt that in 1850, and, perhaps 
in 1849, it might have been detected in our rivers, if dili- 
gently sought for, it does not appear to have attracted the 
notice of Watermen and the staff of Fen Officials, whose 
when it was noticed in considerable quantities all the way 
from Small Bridges down to Bottisham Lock, but not to 
: ger to be sought for, it may be 
found everywhere, in more or less quantity, from Cambridge 
downwards, choking up the mouths of docks, sluices, and 
