1920] St. John,— Elodea in New England 19 
ing year, on Mr. Babington asking what had become of the stick 
which marked the site of the plant, he was informed that it had 
spread all over the ditch. From this point it doubtless escaped, by 
the waste pipe, across the Trumpington Road into the 'Vicar's 
Brook,’ and thence into the river above the mills, where it is now found 
in the greatest profusion. In the case of the Cam, then, we see it 
proved to demonstration, that the short space of four years has been 
sufficient for one small piece of the Anacharis to multiply so as to 
impede both navigation and drainage. When Professor Gray, of 
Boston, U. S., was at Cambridge, Mr. Babington mentioned the 
circumstances to him, at which he expressed surprise, as the Anacharis 
is not found to spread in this active manner in America. Perhaps 
our sluggish streams, the decomposing vegetable and animal matters 
in our Cambridge waters, and especially the excess of lime present 
(fifteen to seventeen grains in the gallon), furnishing an inexhaustible 
supply of inorganic food, may account for its more rapid increase 
here than in America." 
It is noteworthy that with the exception of two stations in eastern 
Massachusetts, Lake Quannapowitt, Wakefield, Andover, and a third 
near Providence, Rhode Island, we know the true Elodea canadensis 
in New England only from western Vermont, Berkshire County, 
Massachusetts, and western Connecticut, regions abounding in lime- 
stone strata. Marshall's suggestion that the limy nature of the 
waters in England may be the factor so favorable for its rapid growth 
and dispersal, receives interesting confirmation from the rarity of 
Elodea canadensis in America in regions that are not decidedly limy. 
“The American weed! (Anacharis Alsinastrum) is causing a great 
amount of anxiety here on account of its amazing growth, and the 
tenacity with which it clings to those spots where it once takes pos- 
session. There is a beautiful sheet of water, of about eighty acres, 
through which the river Trent passed previous to the year 1853, 
when its channel was diverted, but there are still places where the 
connection is maintained, although but slightly so. About three 
years ago the Anacharis first made its appearance in the river, a short 
distance above the lake; it had previously taken possession of the 
Trent and Mersey Canal, with which there are means of communi- 
cation, and a month afterwards it was visible in the lake. Both 
1 Marshall, W., The American Water-Weed. Phytologist n. s. ii. 195 (1857-8). 
