PONDWEED FAMILY 



20. Potamogeton Hillii Morong. Hill's 

 Pondweed. (Fig. 161.) 



Pi>tani(>i;'t'ti>H Hillii Morong, Coult. Bot. Gaz. 6: 290. 1881. 

 Stems slightly compressed, slender, widely branch- 

 ing, i-2 long. Leaves linear, acute or cuspidate, or 

 often almost aristate, i'-2#' long, Y*"-\}" wide, 

 3-nerved, the lateral nerves delicate and nearer the 

 margins than the midrib; stipules whitish, many- 

 nerved, obtuse, 3 // -5 // long; peduncles about ]/ 2 f long, 

 erect or slightly recurved, more or less clavate; spikes 

 capitate, 3-6-fruited; fruit obliquely obovoid, obtuse 

 at the base, about 2" long, i // -iX // 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 New York to Michigan. There are 

 two forms of the species, the one 2-glandular at the base 

 of the leaves, the other glandless. July-Sept. 



21. Potamogeton foliosus Raf. Leafy Pondweed. 



Pobtmogeton foliosut Kaf. Mvd. Rep 'Us 



354- 1808. 

 Potamogeton paucijlorut I'ursh. n Am. Sept 



121. iSi4. Not Lain 



Stems flattened, much branched, l -3* 

 long. Leaves i'-*' lonn. V'-t" wide, 

 acute, 3-nerved, not glandular at the hue; 

 stipules white, hyaline, obtuse or some- 

 times acute, 6"-io" long; peduncles more 

 or less clavate, erect, about #' long; spikes 

 about 4-flowered; fruit lenticular or nearly 

 orbicular, about i" in diameter, 3-keeled 

 on the back, the middle keel winged, sin- 

 uate-dentate, often with projecting shoul- 

 ders or teeth at each end, the face strongly 

 angled or arched, sharp, often with a pro- 

 jecting tooth at the base; style apical. 



In ponds and - 



British Columbia, south t<> Florida. New- 

 Mexico and California. July 



Potamogeton foliosus Niagarensis (Tuckerm. ) Morong. Mem. Torr. Club. 3: Part a, 39. 1895. 



>geton Xiagarensis Tuckerm. Am. Joura. Sci. l II. i 7 : ,vM 

 Larger. Stems 2-3 long, leaves sometimes over r in length and 

 larger and occasionally acute; spikes 8-i2-flowered. Niagara Falls to Michigan 



22. Potamogeton obtusifolius Mert. <X: 

 Koch. Blunt-leaved Pondweed. (Fig. 163.) 

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



Not L. 1753. 

 Potamogeton obtusifolius Mert. & Koch, Deutsch. Fl. 



1:855. 1823. 



Stems usually slender, compressed, widely 

 branching, especially above. Leaves linear, 2'-3 r 

 loug, y^'-i" wide, obtuse, often inucronatc, usually 

 3-nerved with a broad midrib, sometimes 5-7-nerve<!, 

 2-glandular at the base, the glands large and trans- 

 lucent; stipules white or scarious, many-nerved, ob- 

 tuse, 6 // -9 // long, often as long as or longer than the 

 internodes; peduncles numerous, I'-i ';>' long, slen- 

 der, erect; spikes 3 // -4 // long, ovoid, 5-8-flowered; 

 fruit obliquely obovoid, about i#" long and i" 

 thick, 3-keeled ; style short, blunt, nearly facial. 



In still -water, Quebec to Pennsylvania, west to Min- 

 nesota and Wyoming. Also in Europe. July- Aug. 



