18 Rhodora [FEBRUARY 
thread, sheathed at base with a long spathe, the ovary sessile, the 
style elongate, the 3 stigmas two-parted, the 3 stamens cordate, 
borne on thick filaments opposite the outer of the 6 perianth lobes, 
and the leaves in whorls of 3, oblong and obtusish. According to 
Caspary it appears from the data with the specimens that they were 
found near Montreal, while the published statement is brooks of 
Canada (“in rivulis Canadae"). There are six specimens, two of 
them with flowers. 
By some unknown agency this species was introduced into Europe 
where it was found at Warringstown, Ireland,’ in 1836 by a gardener, 
John New. In 1842 it appeared in the lake of Dunse Castle, Ber- 
wickshire, Scotland, and near Dublin, Ireland; in 1847 in the Foxton 
Locks near Market Harborough, Leicestershire, and at Chichester, 
Hampshire, England. "This strange exotic was cultivated in the 
botanical gardens on the continent, and it soon spread to the adja- 
cent rivers and canals and now is one of the commonest hydrophytes 
of western Europe. It is now commonly known in England as 
American duckweed, riverweed, waterweed, Babington's curse, water 
thyme, choke pondweed; in Ireland as cat's tails; in France as élodée 
du Canada; in Germany as Wasserpest, kanadische Wasserpest; in 
Holland as waterpest, engelsch ruigt, professerskruid, studentenroet ; 
in Denmark as Vandpest; in Sweden as Vattenpest; and in Italy as 
peste d'acqua. Most of these names have an uncomplimentary 
connotation, the plant being either a weed or a pest. It is difficult 
for a botanist who has searched for this water plant in New England, 
and perhaps succeeded a few times in finding it in the western parts 
of Vermont, Massachusetts, or Connecticut, to think of it as a serious 
water pest. It is uncommon or local, and certainly not a trouble- 
some weed, but when introduced into Europe it spread like wild fire 
and became a serious menace to drainage and navigation through 
choking up the rivers and canals. Two well authenticated cases are 
quoted to illustrate this. “In 1847 a specimen? from the Foxton 
Locks was planted in a tub, in the Cambridge Botanical Garden; 
and in 1848 the late Mr. Murray, the Curator, placed a piece of it 
in the conduit stream that passes by the new garden. In the follow- 
1 Horn, P., Ueber die sogenannte ‘‘ Wasserpest'' (Elodea canadensis Casp.). Archiv 
der Pharmacie (or Deutscher Apotheker-Vercin) 3rd ser. i. 51—68 (1872); Zur Ent- 
wicklungsgeschichte der Blüthe von Elodea canadensis 426—433 (1872). 
? Marshall, W., Excessive and noxious Increase of Udora Canadensis (Anacharis 
Alsinastrum). Phytologist iv. 714 (1851). 
