PONDWEED FAMILY. 
20. Potamogeton Hillii Morong. Hill's 
Pondweed. (Fig. 161.) 
Potamogeton Hillii Morong, Coult. Bot. Gaz. 6: 290. 1881. 
Stems slightly compressed, slender, widely branch- 
ing, 1°-2° long. Leaves linear, acute or cuspidate, or 
often almost aristate, 1/-24{’ long, '%’/-1{’’ wide, 
3-nerved, the lateral nerves delicate and nearer the 
margins than the midrib; stipules whitish, many- 
nerved, obtuse, 3/’-5’’ long; peduncles about 14’ long, 
erect or slightly recurved, more or less clavate; spikes 
capitate, 3-6-fruited; fruit obliquely obovoid, obtuse 
at the base, about 2’” long, 1’/’-14%’’ 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 folidsus Raf. Leafy Pondweed. (Fig. 162. ) 
Potamogeton foliosus Raf. Med. Rep. (II.) 5: 
354. 1808. 
Potamogeton paucifiorus Pursh, Fl. Am. Sept. 
121. 1814. Not Lam. 1789. 
Stems flattened, much branched, 1°-3, 
long. Leaves 1/-2’ long, 1%’/-1’’ wide, 
acute, 3-nerved, not glandular at the base; 
stipules white, hyaline, obtuse or some- 
times acute, 6’’-10’’ long; peduncles more 
or less clavate, erect, about 14’ long; spikes 
about 4-flowered; fruit lenticular or nearly 
orbicular, about 1// 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 streams, New Brunswick to 
British Columbia, south to Florida, New 
Mexico and California. July-Aug. 
Potamogeton folidsus Niagarénsis (Tuckerm.) Morong, Mem. Torr. Club, 3: Part 2, 39. 1893. 
Potamogeton Niagarensis Tuckerm. Am. Journ. Sci. (II.) 7: 354- 1849. 
Larger. Stems 2°-3° long, leaves sometimes over 3’ in length and 1'’ wide, 3-s-nerved; stipules 
larger and occasionally acute; spikes 8-12-flowered, Niagara Falls to Michigan and California, 
22. Potamogeton obtusifolius Mert. & 
Koch. Blunt-leaved Pondweed. (Fig. 163. ) 
Potamogeton compressus Wahl. Fl. Suec. 1: 107. 1824. 
Not L. 1753. 
Potamogeton obtusifolius Mert. & Koch, Deutsch. FI. 
1: 855. 1823. 
Stems usually slender, compressed, widely 
branching, especially above. Leaves linear, 2/—3/ 
long, '4’/-2’’ wide, obtuse, often mucronate, usually 
3-nerved witha broad midrib, sometimes 5~7-nerved, 
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’—1!s’ long, slen- 
der, erect; spikes 3/’-4’” long, ovoid, 5-S-flowered; 
fruit obliquely obovoid, about 114’ long and 1/ 
thick, 3-keeled ; style short, blunt, nearly facial. 
In still water, Quebec to Pennsylvania, west to Min- 
nesota and Wyoming. Alsoin Europe. July-Aug. 
