PI. end. ph. 
6. FLUVIAT. 26. Potamogit. 35 
Potamogeton setaceum, Lin. S. P. 184 ? 
Potamogeton lanceolatum, Eng. Hot. 1985. 
Potamogeton gramineum, Wahl. FI. Lapp. 52. 
Mountain lakes; perennial; July and August. 
Root creeping; stem floating, branched, slender, round; 
leaves bluntish, thin, flat, 1 -ribbed, reticulately veined; 
stipida involute, tubular, acute ; peduncles single, as long as 
the leaf; spike 8 to 12-flowered; flowers small. 
7. Potamogilon perfoliatum. Thorow riverweed . 
Leaves cordate, amplexicaul, shining, singleribbed ; stem 
round, recurved. 
Potamogiton perfoliatum, Raii 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 ; stipules 
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. seu Fontinalis media lucens, Raii. Syn. 149, 6. 
Tribulus aquaticus minor, muscatellae floribus, 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; stipules broader than the 
leaves. 
P. caule compresso, folio graminis eanini, Raii 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. 
|3. oppositifolium. Stem-leaves opposite. 
y. majus. Leaves larger and broader than usual. 
D 2 
