1 6 :me.moirs of the new york botanical garden. 



It resembles somewhat the preceding, but lacks the floating leaves 

 At an altitude of about 2000 m. 



Yellowstone Park: Clifford R/c/iardsoii, ace. to Morong. 



* Potamogeton foliosus Raf . Med. Rep. II, 5 : 354 [Morong, Mon. 39 ; 



111. Fl. I : 73] : Potamogeton -pauciforiis Pursh, Fl. Am. Sept. 



121 [Bot. Cal. 2: 197]. Not Lam. 



It resembles much P. piisilliis, but has very short spikes and pe- 

 duncles, and lacks propagating buds and glands. In ponds and slow 

 streams, up to an altitude of 2000 m. 



Montana: Butte, July 31, 1895, Rxdbcrg: Bitter-root Valley, 

 1880, Wats-oii. 



* Potamogeton obtusifolius Mert. & Koch, Deutschl. Fl. i : 855 [Mo- 



rong, Mon. 40 : 111. Fl. i : 73] ; Potaiiiogrton rojiiprcssns Wahl. 



Fl. Suec. I : 107. 



It is characterized by its narrow, linear, obtuse leaves and free 

 stipules. In still water up to an altitude of 2000 m. 



Yellowstone Park : Shoshone Geyser Basin, Clifford Richard- 

 son^ ace. to Morong. 



* Potamogeton diversifolius Raf. Med. Rep. (II.) 5: 354 [Morong, 



Mon. 48; 111. Fl. i: 76]. 



It has adnate stipules as the three preceding species, but differs in 

 the presence of floating leaves, which resemble somewhat those of P. 

 natvns, but are much smaller. In still water, up to an altitude of 

 1000 m. 



Montana: Sand Coulee, 1891, P. S. Williams, Sjj. 



Potamogeton filiformis Pers. Syn. PI. i: 152 [Morong, Mon. 50; 



111. Fl. I : 77] ; Potamogeton marinus Coulter, Man. R. M. 364 



[Bot. Cal. 2: 198]. 



In streams, at an altitude of 1000 to 2500 m. The tvpical form is 

 apparently rare. 



Yellowstone Park: Aug., 1884, F. Tzccedy, 2jo, 2ji. 



Potamogeton filiformis occidentalis (Robbins) Morong, Mem. Torr. 

 Bot. Club, 3; part 2, 51, Potamogeton marinas occidentalis Rob- 

 bins, Bot. King Exped. 339 [Bot. Cal. 2 : 198]. 

 This is more common than the type. 



Montana: Bitter Root Valley, 1880, Watson; Missoula, 1880, 

 Watso)i . 



