Genus i. 



PONDWEED FAMILY. 



11 



5. Potamogeton epihydrus Raf. Nuttall's Pondweed. Fig. 178. 



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



1808. 

 Potamogeton Nuttallii Cham. & Schl. Linnaea, 2 : 



226. pi. 6. f. 25. 1827. 

 Potamogeton Claytonii Tuckerm. Am. Journ. Sci. 



45: 38. 1843. 



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

 ing leaves opposite, elliptic to obovate, obtuse, 

 short-petioled, i4'— 34' long, 4"-i2" wide, many- 

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

 long, 1 "-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'-s' long; 

 spikes i'-l' long; fruit round-obovoid ii"-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. 

 June-Aug. 



6. Potamogeton alpinus Balbis. Northern Pondweed. 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 i'-s' 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'-i2* long, 2"-q" 

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

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

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

 dish, ii" long, 1" 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 Pondweed. Fig. 180. 



Potamogeton fluitans Roth, Fl. Germ. 1: 72. 1788? 

 Potamogeton americanus Cham. & Schl. Linnaea, 2 : 



226. 1827. < 

 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'-8'. in 

 length ; submerged leaves pellucid, 4'-i3' long, a"-i2" 

 wide, rounded at the base or tapering into a petiole 

 1-4' long; stipules l'-d,' long, acuminate, acute or 

 obtuse, strongly or faintly 2-carinate; peduncles 

 thickening upward, 2-5' 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. 



