Pl.end.ph, 6. FLUVIAT. 26. Potamogit. 35 



Po(amogeton sefaceuin, Lin. S. P. 184 ? 

 Potamogeton lanceolatiiin, Eng. Bot. 1985. 

 Potamogeton gramineum, Wahl. Fl. Lapp. 52. 



Mountain lakes ; perennial ; July and August. 



RoQl creeping ; stem floating, branched, slender, round ; 

 leaves bluntish, thin, flat, l-ribbed, reticulately veined; 

 stipida involute, tubular, acute; peduncles single, as long as 

 the leaf; spike 8 to 12-flowered ; flowers small. 



7. Potamogiion perfoliatum. Thorow riverweed. 

 Leaves cordate, amplexicaul, shining, singleribbed ; stem 



round, recurved. 



Potamogiton perfoliatum, Rail Syn. 149, 4. 

 Pot. tertium Dodonaei, Ger. em. 822. 



Rivers and ponds ; perennial ; July, August. 



Stem subdichotomous, alternately branched ; leaves 

 brittle, pellucid, very smooth, nearly all alike ; stipidce 

 none ; spike erect, oblong, brown. 



8. Potamogiton densum. Close riverweed, 

 leaves ovate, pointed, opposite, crowded ; stem round, 



forked ; spike usually 4-flowered ; peduncle slender, ter- 

 minal. 



P. sen Fontinalis media lucens. Rail Syn. 149, 6. 



Tiibulus aquaticus minor, muscatellae Horibus, Ger. em. 823. 



Trib. aquaticus minor alter, Park. 1248. 



Potamogeton densum, Lin. S. P. 182. 



Lesser water caltrops. Frogs^ lettuce. 



Still and slow moving waters ; perennial ; June. 

 Herb sunk ; stem closely leaved ; spike sometimes 2-flow- 

 ered, pale green. 



9. Potamogiton compressum. Flat riverweed. 

 Leaves linear, obtuse, with 2 glands at the base ; stem 



compressed; spike fewflowered; stipulce broader than the 

 leaves. 



P. caule compresso, folio graminis canlni, Rail Syn. 149,8, 

 Potamogeton compressum, Lin. S. P. 183. 



Ditches and slow running water ; perennial ; June, July. 



Stem bent ; leaves pale green, alternate; peduncle 

 flattened, rising above the water, 4 or 6-flowered, in distant 

 pairs. 



^. oppoiitijblium. Stem-leaves opposite. 

 7. majus. Leaves larger and broader than usual. 

 d2 



