Part 1, 1909] ZANNICHELLIACEAE 25 
31. Potamogeton compressus I,. Sp. Pl. 127. 1753. 
Potamogeton zosteraefolius Schum. Enum. Pl, Saell. 1: 50. 1801. 
Potamogeton complanatus Willd. Ges. Nat. Freunde Berlin Mag. 3: 297. 1809. 
Potamogeton cuspidaius Schrad.; Smith, Engl. Fl. 1: 234. 1824. 
Stems flattened, sometimes winged, branched, mostly with propagating buds; leaves 
all submerged, linear, 5-20 cm. long, 2-4 mm. wide, the apex acute, cuspidate, or obtuse ; 
primary nerves 3, with numerous secondary and intermediary nerves; stipules scarious, 
axillary and free from the leaf-bases, fugacious, obtuse, 1-3.5 cm. long; spikes cylindric, 
many-flowered, often interrupted, 1-2.3 cm. long; peduncles as thick as the stem, 4-10 cm. 
long; nutlets smooth, 3-keeled, the lateral keels smaller than the toothed or undulate 
middle one; embryo a complete spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: Europe. 
DISTRIBUTION: New Brunswick to British Columbia, south to New York and Oregon. 
ILLUSTRATIONS: Mem. Torrey Club 3?: #1. %; Britt. & Brown, Ill. Fl. £ 160; Linnaea 2: 
bl. 4, f. 10 (alias P. zosteraefolius); Engler, Pflanzenreich 41: f. 24 a-c. 
s 
32. Potamogeton obtusifolius Mert. & Koch; Roehling, Deuts. FI. 
ed. 3.1: 855. 1823. 
Potamogeion compressus Wahl. Fl. Suec. 1: 107. 1824. Not P. compressus I,. 
Stem slender, branched, sometimes with propagating buds; leaves all submerged, 
linear and with 2 glands at the base, acute or obtuse at the apex, 5-8 cm. long, 1.9-3 mm. 
wide, mostly 3-7-nerved, the midrib often compound; stipules whitish, scarious, often 
fugacious, obtuse or acute at the apex, 1.2-2 cm. long; spikes many-flowered, cylindric, 
2-4 cm. long; peduncles as thick as the stem or thicker, 1.2-2.5 cm. long; nutlets very 
slightly pitted, 3-keeled, the middle keel prominent and smooth; style short, blunt ; 
embryo a complete spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: Germany. 
DISTRIBUTION : Quebec to Minnesota, south to northern New York and Kansas. 
Tr a Britt. & Brown, Ill. Fl, f. 167; Mem. Torrey Club 3?: fl. #8; Fl. Dan. 
pl. 2107. 
33. Potamogeton rutilus Wolfg.; R. & S. Syst. Veg. 
Mant. 3: 362. 1827. 
Stem slender, much branched, without propagating buds; leaves all submerged, capil- 
lary; with 2 glands at the base, 2.5-4.6 cm. long, 0.2-0.7 mm. wide, acute or more or less 
pungent at the apex, 3-5-nerved, the midrib often compound ; stipulesacute, 1-2 cm. long, 
or often longer than the internodes, axillary and free from the leaf-bases, sometimes split- 
ting into shreds; spikes scarcely 1 cm. long, few-flowered, sometimes interrupted; pedun- 
cles as thick as the stem, 1-2.3 cm. long; nutlets smooth, without keels but sometimes 
obscurely grooved ; embryo an incomplete spiral, the straight apex pointing outside the 
base. 
TYPE LOCALITY: Vilna, Russia. ; 
DISTRIBUTION : Quebec to Lake Superior, south to New York. . 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. 7. 165; Engler, Pflanzenreich 4: f. 27/, 
34. Potamogeton pusillus L. Sp. Pl. 127. 1753. 
Potamogeton pusillus vulgaris Fries, Novit. ed. 2. 48. 1828. 
Potamogeton pusillus gemmiparus Robb. in A, Gray, Man. ed. 5. 489. 1867. 
Potamogeton gemmiparus Morong, Bot, Gaz. 5: 51. 1880. 
Potamogeton pusillus polyphylius Morong, Bot. Gaz. 5: 51. 1880. 
Potamogeton pusillus panormitanus A. Benn. Jour. Bot. 19: 67. 1881. 
Potamogeton pusillus Sturrockii A. Benn. Jour, Bot. 21: 279. 1883. 
Potamogeton pusillus elongaius A. Benn.; Macoun, Cat. Can. Pl. 5: 371. 1890. 
Potamogeton pusillus capiiatus A. Benn, Jour. Bot. 39: 201. 1901. 
Poitamogeton pusilius pseudo-rutilus A. Benn. Jour. Bot. 39: 201. 1901. 
Potamogelon strictifoluus A. Benn. Jour. Bot. 40: 148. 1902. 
Stem slender, much branched, with propagating buds; leaves all submerged, linear 
or capillary, either slender and recurved or stiff and erect, 2-12 cm. long, 0.1-1.5 mm. 
wide, the apex obtuse, acute or mucronate, the base with 2 small glands; primary nerves 
1-3, often reticulated between, or the whole leaf apparently nerveless ; stipules axillary and 
