Jan. 1908. } POTAMOGETON PENSYLV.ANICUS. 311 
The following was elected a Resident Fellow :— 
Mr. D. W. THomson. 
The following communications were read :— 
POTAMOGETON PENSYLVANICUS, CHAM, ET SCHLECHT., INTRO- 
DUCED TO ENGLAND. By ARTHUR BENNETT, F.LS. 
So far as | know no authenticated case of the introduction 
to the British Isles is known of a species of Polamoyeton, and 
elsewhere we have no knowledge of such, the supposed case 
of P. crispus to N. America! having proved to be an error; 
though there is evidence that c7ispws has been introduced from 
the east coast of the United States to Arizona, suggested by 
the late Dr. Morong as due to the agency of birds. 
What seems to be an undoubted case is the finding of the 
above well-known N. American species by Miss Vigurs 
in a canal at Salterhebble Bridge, near Halifax, Yorkshire, 
in July 1907. Her brother, Dr. Vigurs of Newquay, Corn- 
wall, kindly sent me three sheets so collected, and added, 
“T can make nothing of the pondweed.” 
It is a species that has had many names. By the earlier 
American botanists—Michaux, Pursh, Rafinesque, etc.—it 
was called natans var. 6, fluitans, heterophyllus, ete., and 
no definite name came to be accepted until Professor 
Tuckerman described it very fully under the name of P. 
Clayton in the “American Journal of Science and Art,” 
ser. 1, xlv. 38, 1843. But many years before this Bernhardi 
had sent specimens to Wolfgang, who described it as 
P. pumilus in Roemer and Schultes’ “Syst. Mant.,” i. 354, 
(1827). At about the same time, but really earlier in that 
year (in April), Chamisso and Schlechtendal in their 
monograph of the genus in “ Linnea,” ii. (1827), described a 
P. pensylvanievs from Philadelphia which Willdenow had 
in his herbarium, Tuckerman when in Europe saw these 
specimens at Berlin, and initialed them as his Claytonii. 
Still nothing came of this until 1885, when Dr. Eichler (the 
then Curator) sent me all the specimens of the genus in 
Willdenow’s collection. This and the study of Rafinesque’s 
1 Morong, “ Mon. N. American Naiadace.” 
