26 NORTH AMERICAN FLORA [VoLuME 17 
free from the leaf-bases, hyaline, 0.5-1.5 cm. long, the apex obtuse, or mucronate with the 
extreme tip aristate; spikes cylindric and interrupted or capitate; peduncles as thick as 
the stem or thinner, 1-5 cm. long, erect or recurved; nutlets smooth or ultimately pitted, 
distinctly 3-keeled, or without keels and with 2 grooves on the back of the nutlet, the keels 
or edges of the grooves smooth; style never exceeding 1 mm., straight or recurved; em- 
bryo a complete spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: Europe. 
DISTRIBUTION: Nova Scotia to British Columbia, south to Louisiana, southern California, 
and northern Mexico. 
ILLUSTRATIONS: Mem. Torrey Club 3?: pl. 53,54; Britt. & Brown, Ill. Fl. f. 168, 169; Engl. 
Bot. fl. 215; Fl. Dan. pl. 1451. 
‘The forms listed in the above synonymy are all more or less distinctly, if inconstantly, variable 
from the type. But the variations are all of a vegetative character, and therefore not sufficient for 
specific recognition. 
35. Potamogeton foliosus Raf. Med. Repos. II. 5: 354. 1808. 
Potamogeton gramineus Michx. Fl. Bor. Am. 1: 102. 1803. Not P. gramineus I,. 1753. 
? Potamogeton exstipulatum Muhl, Cat. 18, 1813. 
Potamogeton paucifiorus Pursh, Fl. Am. Sept. 121, 1814. 
Potamogeton niagarensis Tuckerm. Am. Jour, Sci. II. 7; 354. 1849. 
Potamogeton foliosus niagarensis A. Gray, Man. ed. 2. 435. 1856. 
Potomogeton foliosus caltfornicus Morong, Bot. Gaz. 10: 254, 1885. 
Potamogeton californicus Piper, Contr. U. S. Nat. Herb. 11: 98. 1906, 
Stems flattened, much branched, very rarely with propagating buds; leaves all sub- 
merged, linear, 1.5-8 cm. long, 0.4-2 mm. wide, with an obtuse or more or less pungent 
apex, 3-5-nerved, the midrib prominent; stipules axillary and free from the leaf-bases, 
obtuse or acute, 1.3-2.4 cm. long; spikes few-flowered, usually not more than 12 nutlets 
maturing; peduncles usually 1-2 cm. long, as thick as or thicker than the stem; nutlets 
pitted, 3-keeled, the middle keel winged and more or less dentate ; embryo an incomplete 
spiral, the apex pointing towards the base or outside it. 
TYPE LOCALITY : Carolina. . 
DISTRIBUTION: New Brunswick to British Columbia, south to Florida and Mexico; also in 
Cuba, Porto Rico, and Jamaica, 
ILLUSTRATIONS : Britt. & Brown, Ill. Fl. f. 162; Mem. Torrey Club 3?: p/. 47. 
36. Potamogeton confervoides Reichenb. Ic. Fl. Germ. 7: 13. 1845. 
Potamogeton trichotdes A. Gray, Man. 457. 1848. Not. P. trichoides Cham. & Schlecht. 1827, 
Potamogeton Tuckermani Robb. in A, Gray, Man. ed. 2. 434. 1856. 
? Potamogeton Curtistt Morong, Bull. Torrey Club 13: 145. 1886. 
Stems very slender, branched, often dichotomous above, without propagating buds; 
leaves all submerged, linear or capillary, and very slender, 2.5-4 cm. long, scarcely 0.2 mm. 
wide, 1-3-nerved, usually with cross reticulations; stipules delicate, scarcely 5 mm. long, 
acute or obtuse and often splitting into shreds; spikes globose or subglobose, 5-8 mm. long, 
few-flowered ; peduncles often branched, somewhat thicker upward, 2.5-12 cm. long; nut- 
lets pitted, 3-keeled, the middle keel prominent and crisped or dentate; embryo a complete 
spiral, the curved apex pointing inside the base. 
TYPE LOCALITY: Alleghany Mountains. 
DISTRIBUTION : New England to New Jersey and Pennsylvania, apparently also in Florida 
£. Curtisté 
; a a Britt. & Brown, Ill. Fl. 4. 458; Mem. Torrey Club 3?: J, 42. 
P. Curtisti Morong was described without the mature fruit having beey seen. It is without 
distinctive vegetative characters, and the absence of fruit makes it impossible to determine its 
status accurately. 
SPECIES NOT CHRTAINLY NORTH AMERICAN 
Potamogeton acutifolius Link; R. & S. Syst. Veg. 3: 513 (1818), is found at Lancaster, 
Pennsylvania, according to A. Bennett (Jour. Bot. 39: 200), Asingle specimen in the Munich 
Herbarium, supposed to have been collected by Muhlenburg, is cited. The species is 
unknown in America except for this. It is otherwise known from Asia and Australia. 
