24 NORTH AMERICAN FLORA [VoLUME 17 
27. Potamogeton filiformis Pers. Syn. Pl. 1: 152. 1805. 
Potamogeton marinus L,. Sp. Pl. 127, in part. 1753. 
Potamogeton marinus Macounti Morong ; Macoun, Cat. Can. Pl. 4: 88. 1888. 
Stem slender, much branched, scarcely 5 dm. long; leaves all submerged, capillary, 
the apex more or less pungent, 5-20 cm. long, 0.2-0.4 mm. wide, mostly 1-nerved ; stipules 
adnate to the leaf-bases, the sheath scarcely 5 mm. long, the free part scarious-margined 
and much longer; spikes slender, often much interrupted ; peduncles very slender, 7-20 
em. long; nutlets scarcely 1.7 mm. long, smooth, mostly without keels, the style almost 
invisible; embryo a complete spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: Europe. 
DISTRIBUTION : Quebec to the Northwest Territory, south to New York and Montana. 
ILLUSTRATIONS : Mem. Torrey Club 3?: £1. 57; Britt. & Brown, Ill. Fl. 4. 172; Linnaea 2: pl. 
4, Fi 3: 
28. Potamogeton interior Rydb. Fl. Colo. 13. 1906. 
Potamogeton marinus occidentalis Robb. in S. Wats. Bot. King’s Expl. 339. 1871. 
Potamogeton filtformis occidentalis A. Benn. Ann. Conserv. Jard. Genéve 9: 102. 1905. 
Stem slender, much branched and longer than in the preceding; leaves all submerged, 
capillary or narrowly linear, with an acute or more or less pungent apex, 5-15 cm. long, 
0.3-1 mm. wide, mostly 1-nerved; stipules adnate to the leaf-bases, the sheath at least 1 
em. long, the free part shorter; spikes few-flowered, often interrupted, 1-3.5 cm. long; 
peduncles as thick as the stem, 3-18 cm. long; nutlets sometimes slightly pitted, without 
keels or inconspicnously 1-keeled; style almost invisible ; embryo an incomplete spiral, the 
straight apex pointing directly towards the base. 
TYPE LOCALITY: Ruby Lake, Nevada. : 
DISTRIBUTION : Ontario to the Northwest Territory, south to Utah and Colorado. 
29. Potamogeton Friesii Rupr. Beitr. Pfl. Russ. 
Reich. 4: 43. 1845. 
Potamogeion compressus Oeder, Fl. Dan. £1. 203. 1765. Not P. compressus I. 
? Potamogeton mucronatus Schrad.; R. & S. Syst. Veg. 3: 517. 1818. 
Potamogeton pusillus major Fries, Novit. ed. 2. 48. 1828. 
Potamogeton major Morong, Mem. Torrey Club 3?: 41. 1893. 
Stem compressed, branched ; leaves all submerged, linear, 4-7 cm. long, 2-3 mm. wide, 
the apex acute or obtuse, 5-7-nerved, and with 2 small glands at the base of the leaf; 
stipules axillary and free from the leaf-bases, 1.2-2.3 cm. long, whitish and many-nerved, 
acute or obtuse at the apex; spikes few-flowered, 1-4 cm. long, often interrupted; peduncles 
as thick as the stem, often thickening upwards, 2-4 cm. long; nutlets pitted, 3-keeled or 
without keels and with 2 distinct grooves on the back, the keels when present smooth ; 
embryo an incomplete spiral, the straight apex pointing towards the base or outside it. 
TYPE LOCALITY: Russia. 
DISTRIBUTION: Nova Scotia to North Dakota, south to New York and Iowa. 
ILLUSTRATIONS: Mem. Torrey Club 3?: f/. 49; Britt. & Brown, Ill. Fl. f. 164 ; Engler, Pflan- 
zenreich 41): f. 27 e (as P. mucronatus); Engl. Bot. pl. 418 (as P. compressus). 
30. Potamogeton Hillii Morong, Bot. Gaz. 6: 290. 1881. 
Stem slender, branched, without propagating buds; leaves all submerged, linear, acute, 
cuspidate or aristate at the apex, 2.5-6 cm. long, 2-2.8 mm. wide, with 2 glands at the base 
or glandless, 3-nerved, the lateral nerves less prominent than the midrib and remote from 
it; stipules scarious, 0.6-1.8 cm. long, aristate or rarely obtuse at the apex, axillary and 
free from the leaf-bases ; spikes few-flowered; peduncles scarcely more than 1.5 cm. long, 
as thick as or a little thicker than the stem; nutlets smooth, 3-keeled, the middle keel 
prominent and undulate or crisped, the lateral keels inconspicuous; style projecting at 
least 1 mm. from the body of the fruit and crowned with a depressed-globose stigma ; 
embryo a complete spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: New York and Michigan. 
DISTRIBUTION: New York to Michigan and Lake Superior, south to Pennsylvania and Mis- 
souri. 
ILLUSTRATIONS: Bot. Gaz. 6: 291. f. 3; Mem. Torrey Club 3%: £1. 46; Britt. & Brown, Ill. 
Ff. 161. 
