22 NORTH AMERICAN FLORA [VoLumE 17 
nerves scarcely 1 mm. from it, the secondary nerves 2-5; stipules scarious, fugacious, usually 
splitting into shreds; propagating buds, in our forms, prominent in the axils of decayed 
leaves and at the ends of the branches ; spikes cylindric, 1-1.8 cm. long; peduncles as thick 
as or thicker than the stem, often recurved in fruit; nutlets 3-keeled, the middle keel with a 
single spur-like projection near the base; style projecting at least 2 mm. from the body of 
the fruit; embryo an incomplete spiral, the straight apex pointing directly towards the base. 
TYPE LOCALITY: Europe. 
DISTRIBUTION : Ontario to Delaware and eastern Pennsylvania. Obviously introduced from 
the Old World. 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. f. 169; Mem. Torrey Club 3?: f/. 44; Fl. Dan. #1. 
927 (poor); Engl. Bot. p/. 2012; Engler, Pflanzenreich 41: f, 27 a-c. 
21. Potamogeton praelongus Wolfg. Arch. Bot. Roem. 
3: 331. 1805. 
parolee ane Dethard. (Strelitz. Anzeig. 1809: no. 50?) ; Koch, Syn. Fl. Germ. & Helv. 
Stem flattened, mostly branched; leaves all submerged, mostly perfoliate; blades 
bright-green, the apex cucullate and splitting when dry, lanceolate or lanceolate-oblong, 
5-20 cm. long, 1.5-4 cm. wide, mostly broader below the middle; margins crisped ; primary 
nerves 3-5 with secondary ones often intermediate, transverse nerves sometimes forming 
cellular reticulation along the midrib; stipules usually split into fine shreds when old, 4-35 
mm. long; spikes cylindric or subglobose, 0.9-3 cm. long, many-flowered; peduncles as 
thick as the stem or thicker, 7-25 cm. long; nutlets smooth, 1-keeled or sometimes with 
2 lateral and more inconspicuous keels; embryo an incomplete spiral, the straight apex 
pointing towards the base. 
TYPE LOCALITY: Laiback river, Austria. 
- Mee : Massachusetts to British Columbia, south to Pennsylvania and California ; also 
ILLUSTRATIONS: Mem. Torrey Club 3?: #/. 39; Britt. & Brown, Ill. Fl. f 155, Linnaea 2: 
pl. 5, f. 14; Engler, Pflanzenreich 41; f, 22. 
.22. Potamogeton perfoliatus L. Sp. Pl. 126. 1753. 
Potamogeton crispus Darl. Fl. Cest. 23. 1826. Not P. crispusl,. 1753. 
Potamogeion perfoliatus lanceolatus Robb. in A. Gray, Man. ed. 5. 488. 1867. 
Potamogeton perfoliatus Richardsonit A. Benn. Jour. Bot. 27: 25. 1889, 
Potamogeton Richardsonii Rydb. Bull. Torrey Club 32: 599, 1905. 
Potamogeton bupleuroides Fernald, Rhodora 10: 46. 1908. 
Stems branched ; leaves all submerged, perfoliate ; blades thin and translucent or thick 
and semi-coriaceous, orbicular, ovate or ovate-lanceolate, rounded or acute at the apex and 
always perfoliate at the base, 1-8.5 cm. long, 0.6-2.5 cm. wide; margins crisped or appa- 
rently sometimes smooth, rarely serrulate towards the apex; nerves 1-several, the midrib 
always prominent and sometimes the lateral nerves prominent also; stipules splitting into 
shreds, 0.2-2.5 cm. long, usually clasping the stem ; internodes 1-10 cm. long; spikes cylin- 
dric, 0.5-2 cm. long; peduncles as thick as the stem, usually thickening upwards; nutlets 
with an indentation curving from the edge to the center of the face, thus apparently pitted, 
with a smooth or corrugated epicarp, obscurely 3-keeled, the middle keel more prominent 
than the lateral ones; embryo a complete spiral, the curved apex pointing just inside 
the base. 
TYPE LOCALITY: Europe. 
DISTRIBUTION : Throughout North America, except Mexico and the West Indies; reported 
from Guatemala; also in Europe. 
ILLUSTRATIONS: Engler, Pflanzenreich 41: f. 21, a-{; Mem. Torrey Club 3?: £/. 40, Britt. & 
Brown, Ill. Fl. 7. 156; Engl. Bot. pl. 168. 
Perhaps an aggregate species. Forms occur with lanceolate, acute-tipped leaves, reaching by 
numerous intergradations an orbicular type. Differences of marked, though inconstant, sort are 
found also in the venation of the leaf and the length of the stipules. But the vegetative characters 
are so fugitive, and the essential fruit characters so persistent, that there seems little warrant for 
the maintenance of the species listed in the above synonymy. 
Potamogeton mysticus Morong, Bot. Gaz. 5: 50. 1880. This is apparently a depauperate form 
of the above, confined to Mystic Pond, Medford, Massachusetts. It has never produced fruit and 
may be a hybrid. ; 
