Potamoyeton. NAIADACEyE. 197 



curved. — Keiclienb. 1. c. 22, t. 3G, 37. P. Proteus lucens, Cham, in Linnica, ii. 197, 

 t. 5, tig. IG, a, b. 



In ponds ; at Mission Dolores {Bolander, n. 274) and also collected by CAammo ^nd Kellogg 

 & K"^; rather rare eastward, Ironr New England to Florida and New Mexico, and also 

 European. 



8 P pr^loneus Wulf. Stem stout, elongated, branching and flexuous above: 

 leaves obl..ir-lann.olute or lanceolate, 2 to 10 inches long by 6 to 12 lines broad, 

 obtuse and smnewhat cucullate at the apex, rounded and clasping at base, undulate- 

 serrate ; stipules white and conspicuous, i to 1 inch long: peduncles often much 

 elonoated: fruit semicircular, 2 lines long, acutely keeled, prominently beaked : 

 embryo slender, the cotyledon pointing to the base of the radicle. — Cham. 1. c. i J 1, 

 t. 5, tig. 14 ; Eeichenb. 1. c. 21, t. 33. 



In ponds and deep water ; Sierra County {Lcmmo7i) and eastward, in New England and about 

 the Great Lakes ; also European. Fruit rare and maturing late. 



9 P perfoliatus, Linn. Stem more slender, not flexuous, branching : leaves 

 broadly" cordate to cordate-lanceolate, i to 1^ inches long, obtuse or acute, clasping 

 at base : stipules small and not persistent : spikes rather loose and somewhat coni- 

 pouml, short (3 to 9 lines long, or rarely more), on mostly short peduncies : truit 

 oblong-obovate, nearly U lines long, obtusely keeled, beaked by the short slender 

 style : embrvo as in tlie last. _ 



Var (t) lanceolatus, Uobbins. Leaves longer (2 to 4 inches or more), and more 

 lanceolate, acuminate, undulate : peduncles thickened upward : fruit broader, nearly 

 orbicular. — Gray, Manual, 488. 



The variety only has been collected near the borders of California; TruckeeEiver Nevada 

 ( J V!TlX Oregon and Washington Territory (Lyall, Hall, Ho^veliy m the Yellowstone 

 region (Richardson), and common in the northern Atlantic States, where the typical European 

 form is also found. 



* * * Leaves all mh merged and uniform, Jiarroivb/ linear or setaceous, sessile. 

 H- Stipules free from the narrow base of the leaf 

 ■H- Flowers in a linear cylindrical spike. 

 10 P zostereefolius. Sebum. Stem flattened and somewhat winged, branch- 

 incr . 'leaves grass-like, 3 to 8 inches long by 1 \ lines wide, 3-nerved, abruptly acute, 

 nol narrowed toward the clasping base ; stipules conspicuous, obtuse : spike rather 

 loosely flowered, ^ to 1 inch long, shorter than the peduncle : fruit large (2 lines 

 long) broadly obfong, beaked by the stout style, somewhat undulate-keeled : coty- 

 ledon incurved. — Cham. 1. c. 182, t. 4, fig. 10 ; Keichenb. 1. c. 17, t 27 P. com- 

 2jressus, Fries, not Linn. herb, nor Oeder ; Bobbins in Gray's Manual, 488. 



In still or slow-flowing water ; found in Oregon {Hall, n. 491), and to be expected in Northern 

 California ; in British America and the northern Atlantic States, but not common, and in north- 

 ern Europe. 



H-t- ++ Spike suhcapitate, or (in n. 13) often loose or interrupted. 

 11 P. pauciflorus, Pursh. Stem very slender, flattish, much branched, 8 to 

 20 inches high : leaves narrowly linear, 1- (obscurely 3-) nerved, an inch or two 

 lon^' by rarely half a line wide, acute, narrowed at base ; stipules small, obtuse, be- 

 coming setose : spikes 2- 10-seeded, on very short clavate flattened peduncles : fruit 

 roundfsh, a line long, abruptly beaked by the rather slender straight style, and with 

 a more or less broad undulate-dentate keel : embryo slender, witli incurved cotyle- 

 aoiv — Cham. L c. 176, t. 4, fig. 7. 



In still waters ; near San Francisco (Chamisso, G. F. Vascy) ; Oregon [Hall, Honrll) ; common 

 in the Atlantic States. 



12. P. Niagarensis, Tuckerman. Stem often longer (1 to 3 feet) : leaves 

 larger, U to 3h (about 2) inches long by a line wide or less, 3-5-nerved at base, 



