ZAXXICHELLIACEAE. 



VOL. I. 



20. Potamogeton Hillii Morong. Hill's Pond- 

 weed. Fig. 193. 



Potamogeion Hillii Morong. Coult. Bot. Gaz. 6: 290. iSSi. 



Stems slightly compressed, slender, widely branching, 

 l~-2 long. Leaves linear, acute or cuspidate, or often 

 almost aristate. i'-2i' long, i"-ii" wide, 3-nerved, the 

 lateral nerves delicate and nearer the margins than the 

 midrib: stipules whitish, many-nerved, obr/.se. 3 "-5" 

 long; peduncles about i' long, erect or slightly recurved, 

 more or less clavate; spikes capi::.:e. 3-6-fruited : fruit 

 obliquely obovoid, obtuse at the base, about 2" long. 

 i"-ii" thick. 3-carinate on the back, the middle keel 

 sharp and more or less undulate, flat on the sides, face 

 slightly arched; style nearly facial, short; embryo coiled. 



In ponds, eastern Xew York to Michigan, south to 

 Pennsylvania and Missouri. There are two forms of the 

 species, the one ^-glandular at the base of the leaves, the 

 other glandless. July-Sept. 



21. Potamogeton foliosus Raf. Leafy Pondweed. Fig. 194. 



Po: _ ~ Rep. (II.) 5: 



54. 1808. 



Potamogeion pauciftorus Pursh. Fl. Am. Sept. 

 121. 1814. Xot Lam. 1789. 



;eton niagc . /.ckerm. Am. Journ. 



Sci. (II.) 7- i : -9- 



_ -:liosus niaga Tuckerm.) 



TDng, Mem. Torr. Club, 3: Part 2, 39. 

 1893. 



- .ms flattened, much branched, i = -3 



long. Leaves i'-3' lor- 1 -i" wide, acute, 



nerved, not glandular at the base; 



.- or sometimes 



acute, 6"-io" long; peduncles more or less 

 :-. erect, about \' long; spikes 4-12- 

 flowered ; fruit lenticular or nearlj- orbic- 

 ular, about i" in diameter. 3-keeled on the 

 back, the middle keel winged, sinuate- 

 dentate, often with projecting- shoulders or 

 teeth at each end, the face strongly angled 

 or arched, sharp, often with a projecting 

 tooth at the base; style ap: 



In ponds and streams. Xew Brunswick to 



-h Columbia, south to Florida, Xew Mexico and California. Tuly-Aug. 



1 



22. Potamogeton obtusifolius Mert. & Koch. 

 Blunt-leaved Pondweed. Fig. 195. 



Potamogeton compressus Wahl. Fl. Suec. i: 107. 1824. 



Xot L. 1/53- 

 Potamogeton obtusifolius Mert. & Koch. Deutsch. Fl. 



i : 855. 1823. 



Stems usually slender, compressed, widely branch- 

 ing, especially above. Leaves linear. 2'-$' long, \"-2" 

 wide, obtuse, often mucronate. usually 3-nerved with 

 a broad midrib, sometimes 5-7-nerved, 2-glandular 

 at the base, the glands large and translucent ; stipules 

 white or scarious, many-nerved, obtuse, 6"-o/' long, 

 often as long as or longer than the internodes ; 

 peduncles numerous. i'-ii' long, slender, erect; spikes 

 -4" long, ovoid. 5-8-flowered ; fruit obliquely obo- 

 void, about \\" long and i" thick, 3-keeled: style 

 short, blunt, nearly facial. 



_ In still water. Quebec to Minnesota, south to northern 

 Xew York and Kansas. Also in Europe. Tuly-Aug. 



