373 



THE HALIFAX POTAMOQETON.* 



A. BENNETT, F.L.S., 

 Croydon. 



(The ' ! ' following a record indicates that I have seen the. 

 species). 



Potamogeton pensylvanicus Cham et Sch. Linnaea, ii. (1827), 

 227.! 



P. pumilus Wolfg. Roem et Sch. Mant iii. (1827) 354.! 



P. Claytonii Tuck. Am. Jour. Scie. and Arts ist ser., xiv. 

 {1843), SSJ 



p. epihydvum Rafin. Med. Rep. 2nd Hex. v. (1808), 354. 



P. Nuttalii Cham et Sch. Ic. 226 teste Morong. 



Descrip. Morong. Mon. N. Am. Naid. t. xxix. (1893), 18. 



' Stems slender, compressed, mostly simple, generally from 

 I to 3 feet high, but sometimes 6 feet, according to the depth 

 of the water in which it grows. Floating leaves elliptical, 

 sometimes obovate, obtuse at the apex, sloping at the base 

 into a short petiole 1^-3^ inches long, and 4-12 lines wide, 

 12-27 nerved. These leaves sometimes number as many as 

 4 or 5 pairs at several inches distance from each other in the 

 upper part of the stem. Submerged leaves linear, 2-ranked, 

 2-7 inches in length, and 1-3 lines in width, 5-nerved, the 2 

 inter lateral nerves nearly marginal, the space between the 

 two inner and the midrib evenly and coarsely cellular reticu- 

 lated. In young plants the submerged leaves are often crowded 

 close together, the internodes afterwards elongating. Stipules 

 obtuse, hyaline, nerved, keelless. Peduncules about the 

 thickness of the stem, 1-3 inches long. Spikes J-i inch long, 

 fruiting freely. Fruit roundish-obovate, lines long, by 



i-ij lines broad, 3-keeled, middle keel sharp, the sides flat, 

 and distinctly impressed ; style short, apical, embryo coiled 

 ij times. 



There is a very large form of it — P. Nuttalii var. Cayu- 

 gaensis Wiegand, ! occurring in New York and Canada, f 



In Canada it is distributed from British Columbia ! across 

 to Upper Canada, ! and from Lake Superior north to Sable 

 Island, ! 44° N. Lat., and Lake St. John, 49° N. Lat. In U.S.A., 



* See 'The Naturalist,' January, 1908, pp. lo-ii. 



+ What appears to be another introduction from North America is the 

 recent discovery of Sagittaria heterophylla Pursh. in the river Exe in 

 Devonshire. 



1908 October i. 



B 2 



