14 NORTH AMERICAN FLORA [Volume 17 
1. Ruppia maritima L. Sp. Pl. 127. 1753. 
Ruppia curvicarpa A. Nelson, Bull. Torrey Club 26: 122. 1899, 
? Ruppia pectinaia Rydb. Mem.N. Y. Bot. Gard. 1:18. 1900. 
Stem whitish or green, simple or branched; leaves all submerged, thread-like, 0.3 mm. 
wide or less, 2-10 cm. long with an acute or more or less pungent apex; stipular sheath 
6-10 mm. long, the free part much shorter or wanting; flowers on a short pedicel which 
elongates after anthesis, and is ultimately a loosely coiled spiral; stamens without a fila- 
ment, early deciduous; anthers 2, sessile, 2-celled; mature carpels ovoid, equilateral, or 
gibbous and oblique, about 2 mm. long, stipitate; style short and stout, or finely atten- 
uate, straight or hooked; pedicels of the fruit 1.3-3 cm. long. 
TYPE LOCALITY : Europe. . 
DISTRIBUTION: Atlantic and Pacific coasts of North America, and in saline poolsin the interior. 
ILLUSTRATIONS : Mem. Torrey Club 3?: £1. 62; Britt. & Brown, Ill. Fl. f. 176; Engl. Bot. pi. 
136; E. & P. Nat. Pf. 21: f. 161 e-g. 
Ruppia pectinata Rydb. is a species described as having an equilateral, not oblique, fruit and 
a style that is so short as to be almost wanting. These characters it has in common with many 
plants of R. maritima I,., and it cannot be kept out of that species on these alone. Type speci- 
men not seen by me. 
2. Ruppia occidentalis S. Wats. Proc. Am. Acad. 25: 138. 1890. 
Ruppia lacustris Macoun, Cat. Can. Pl. 5: 372. 1890. 
Stem slender, with divaricately ascending branches; leaves all submerged and linear, 
7-20 cm. long, less than 0.3 mm. wide; stipular sheaths 1.5-3 cm. long, the free part as 
long; flowers similar to the preceding ; mature carpels pear-shaped, tipped by a straight 
style; pedicels of the fruit less than 2.5 cm. long. 
TYPE LOCALITY: Kamloops, British Columbia. 
DISTRIBUTION : From the type locality and from Nebraska. 
ILLUSTRATIONS : Mem. Torrey Club 3?: /. 63, Britt. & Brown, lil. Fl. f. 277. 
3. POTAMOGETON L,. Sp. P1.126. 1753. 
Peltopsis Raf. Jour. de Phys. 89: 101. 1819. 
Spirillus Gay, Compt. Rend. Acad. Sci. Paris 38: 703. 1854, 
Stems submerged or floating, simple or branched, the ends often thickening and form- 
ing propagating buds, which fall off and strike root. Leaves of two kinds, floating and 
submerged, in some species of great variability in width and length. Floating leaves cori- 
aceous or semi-coriaceous, rarely semi-pellucid, usually expanded into a proper blade. 
Submerged leaves sometimes reduced to terete phyllodia, or with a broad or capillary leaf- 
blade. Stipules either free from the leaf-bases, or closely adnate to them. Inflorescence a 
simple or branched spike. Flowers perfect, usually thickly clustered on the sometimes 
interrupted spike. Perianth none. Stamens 4, Anthers 2-celled, the connective much 
enlarged and perianth-like. Gynoecium of 4 distinct, sessile, carpels. Ovules solitary in 
each carpel. Fruit an indehiscent nutlet. Embryo a complete or incomplete spiral, the 
curved or straight apex pointing towards or inside the base. 
Type species, Potamogeton natans L. 
1. With floating and submerged leaves. (Floating leaves rarely wanting in nos. 10, 11, and 12.) 
A. Mature submerged leaves (or phyllodia) narrowly linear, or linear-lanceolate, never more 
than 4mm. wide. aot a 
The straight apex of the embryo pointing towards the base or outside it. 
Submerged leaves reduced to phyllodia; floating leaf-blades more than 3 cm. long. 
Nutlets pitted ; peduncles as thick as the petioles. — 1. P. natans. 
Nutlets smooth ; peduncles twice as thick as the petioles. 2, P. Oakesianus, 
Submerged leaves with a proper blade; floating leaf-blades less : 
than 1.2 cm long. ; 3, P. lateralis. 
The curved apex of the embryo pointing inside the base. ; 
Embryo coiled once, the apex pointing downward. 4. P. Vaseyi. 
Embryo coiled 1% times, the apex transverse or pointing upward. 
Floating leaf-blades less than 2.5 cm. long ; submerged leaves 
without cellular reticulation along the midrib. 
Submerged peduncles 46.5 mm. long; submerged leaves 7 
0.4-0.9 mm. wide. 5. P, diversifolius, 
Submerged peduncles 0.3-1.5 mm. long ; submerged leaves 1- : 
1.4mm. wide. 6, P. dimorphus, 
