288 DR. JOHNSTON ON ANACHARIS ALSINASTRUM. 



plant growing with Potomoc/tton crispum, pusillum, and petfo- 

 Uatum, in the bed of the river, at a depth of about fifteen 

 inches. In the lake at Dunse Castle, the Anacharis had a 

 long slender stem, but here, influenced by the stream, it grew 

 in a roundish tuft or bunch, with stems not exceeding three 

 or four inches in height. None of them rose to the surface, 

 and on none of them were there any flowers. 



On September 4, I again discovered the Anacharis in 

 great abundance, in a small creek at a still and deep reach 

 of the Whitadder, between Whitehall and Edington Mill. 

 Here it had the habit of the plant in Dunse Castle Loch, 

 with stems from two to three feet in length. None of them 

 "were in flower. 



It would be presumptuous for me to say, whether the Ana- 

 charis alsinastrum is identical with the Udora canadensis or 

 not. I have specimens of the latter from Dr. P. W. Macla- 

 gan, gathered in Detroit River, July, 1848, and they resemble 

 exactly our Whitadder plant, as found at the NcAvmills sta- 

 tion ; but, like this, the Canadian specimens have alscf no 

 flowers. I can see no difference of any moment in the shape 

 of the leaves, for this difiers in the British as in the Ameri- 

 can plant ; and the structure and marginal serratures are ex- 

 actly alike. The spinulose serratures begin in both about 

 the middle of the leaf, and are of a brown colour, and firm 

 texture. The apex of the leaf in the Canadian Udora is 

 usually more pointed or lanceolate than of the Whitadder 

 Alsinastrum, but, in an aquatic plant, such a slight character 

 is of no consequence. Pursh, in fact, of the American plant, 

 says : — " Michaux describes the leaves to be oblong and ob- 

 tuse, which is only the case in the early part of the season ; 

 at flowering time they constantly are long linear and acute." 

 — Flor. Amer, Sept. p. 83. 



The American plant is " frequent from Canada to Virginia.'' 

 Dr. P. W. Maclagan writes me, that it is extremely common 

 in Upper Canada, "but I never could make more than one 

 species, although I looked at them well after I got Mr. Ba- 

 bington's paper. Dr. Gray makes but one species in the 

 Northern States.'' Dr. Gray's description of Udora canadensis 

 is as follows : — " A perennial ? herb, growing under water 



