Potamogeton. NAIAD ACE.E. 197 



curved. Reichenb. 1. c. 22, t. 36, 37. P. Proteus lucens, Cham, in Linnsea, ii. 197, 

 t. 5, tig. 16, a, b. 



In ponds ; at Mission Dolores (Bolander, n. 274) and also collected by Ckamisso and Kellogg 

 & Harford; rather rare eastward, from New England to Florida and New Mexico, and also 

 European. 



8. P. praelongus, Wulf. Stem stout, elongated, branching and flexuous above : 

 leaves oblong-lanceolate or lanceolate, 2 to 10 inches long by 6 to 12 lines broad, 

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

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

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

 embryo slender, the cotyledon pointing to the base of the radicle. Cham. 1. c. 191, 

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



In ponds and deep water ; Sierra County (Lemmon) 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, \ to 1^ inches long, obtuse or acute, clasping 

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

 pound, short (3 to 9 lines long, or rarely more), on mostly short peduncles : fruit 

 oblong-obovate, nearly 1| lines long, obtusely keeled, beaked by the short slender 

 style : embryo as in the last. 



Var. (?) lanceolatus, Robbins. 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 ; Truckee River, Nevada 

 ( W. W. Bailey} ; Oregon and Washington Territory (Lyall, Hall, ffowell) ; in the Yellowstone 

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

 form is also found. 



* * * Leaves all submerged and uniform, narrowly linear or setaceous, sessile. 



*- Stipules free from the narroiv base of the leaf. 



H- Flowers in a linear cylindrical spike. 



10. P. zosteraefolius, Schum. Stem flattened and somewhat winged, branch- 

 ing : leaves grass-like, 3 to 8 inches long by 1 \ lines wide, 3 -nerved, abruptly acute, 

 not 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 oblong, beaked by the stout style, somewhat undulate-keeled : coty- 

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

 pressus, Fries, not Linn. herb, nor Oeder; Robbins 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- -H- Spike subcapitate, 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 

 long 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 

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

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

 don. Cham. 1. c. 176, t. 4, fig. 7. 



In still waters ; near San Francisco (Chamisso, G. F. Vasey) ; Oregon (Hall, HowelT) ; common 

 in the Atlantic States. 



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

 larger, 1| to 3| (about 2) inches long by a line wide or less, 3-5-nerved at base, 



