GENUS i. 



PONDWEED FAMILY. 



77 



5. Potamogeton epihydrus Raf. NuttaH's Pond weed. Fig. 178. 



Potamogeton epihydrus Raf. Med. Repos. II. 5 : 354- 



1808. 

 Potamogeton Nttttallii Cham. & Schl. Lmnaea, 2 : 



226. pi. 6. /. 25. 1827. . 



Potamogeton Claytonii Tuckerm. Am. Journ. bci. 



45: 38. 1843- 



Stems slender, compressed, i-6 long. Float- 

 ing leaves opposite, elliptic to obovate, obtuse, 

 sbort-petioled, ii'-3*' long, 4." -12" wide, many- 

 nerved; submerged leaves linear, 2-ranked, 2' -7' 

 long, i "-3" wide, 5-nerved, the 2 outer nerves 

 nearly marginal, the space between the 2 inner 

 and the midrib coarsely reticulated; stipules ob- 

 tuse, hyaline, not keeled; peduncles i'-5' long^ 

 spikes J'-i" long; fruit round-obovoid \\"-2" 

 long, i"-ii" thick, 3-keeled, the sides flat and 

 indistinctly impressed; style short, apical; embryo 

 coiled one and one-third times. 



In ponds and streams, Newfoundland to British 

 Columbia, North Carolina and Iowa. Creek-grass. 

 Jane- Aug. 



6. Potamogeton alpinus Balbis. Northern Pond weed. Fig. 179. 



Potamogeton alpinus Balbis, Misc. Bot. 13. 1804. 

 Potamogeton rufescens Schrad. ; Cham. Adn. Fl. 

 Ber. 5. 1815. 



Plant of a ruddy tinge ; stems simple or branched, 

 somewhat compressed. Floating leaves spatulate 

 or oblanceolate, obtuse, many-nerved, tapering 

 into petioles 1'-$' long; submerged leaves semi- 

 pellucid, the lowest sessile, the uppermost petioled, 

 oblong-linear or linear-lanceolate, obtuse or rarely 

 acute, narrowed at the base, 3'- 12' long, 2"-$" 

 wide, 7-nerved ; stipules broad, faintly 2-carinate, 

 obtuse or rarely acute; peduncles 2 '-8' long; 

 spikes i'-il' long; fruit obovoid, lenticular, red- 

 dish, li" long, i" thick, 3-keeled, the middle keel 

 sharp, the face arched, beaked by the short re- 

 curved style ; apex of the embryo pointing directly 

 to the basal end. 



In ponds, Labrador to British Columbia, Florida 

 and California. Also in Europe. July-Aug. 



7. Potamogeton americanus Cham. & Schl. Long-leaved Pond weed. Fig. 180. 



Potamogeton fluitans Roth, Fl. Germ, i: 72. 1788? 

 Potamogeton americanus Cham. & Schl. Lmnaea, 2: 



Potamogeton lonchites Tuckerm. Am. Journ. Sci. (II.) 



6: 226. 1848. 

 Potamogeton lonchites noveboracensis Morong. Mem. 



Torr. Club, 3: Part 2, 20. 1893. 



Stem terete, much branched, 3-6 long. Floating 

 leaves rather thin, elliptic, pointed at both ends ; 2^-6 

 long, 6"-24" wide, many-nerved, on petioles 2 -j-8 in 

 length; submerged leaves pellucid, 4'-! 3" long, 2' -12 

 wide, rounded at the base or tapering into a petiole 

 i '-4' long; stipules i'-4' long, acuminate, acute or 

 obtuse, strongly or faintly 2-carinate ;_ peduncles 

 thickening upward, 2'-$' long; spikes cylindric, 1-3 

 long; fruit about 2" long, i"-ii" thick, obliquely 

 obovoid. the face nearly straight, the back 3-keeled, 

 the middle keel rounded or often with a projecting 

 wing under the style, not impressed on the sides; 

 embryo slightly incurved, apex pointing slightly in- 

 side of the base. 



In ponds and slow streams, New Brunswick to Wash- 

 ington, Florida, West Indies, and California. July-Oct. 



