7. Potamogeton Americanus Cham. & Schl. Long-Leaved Pondweed

Fig. 180

Potamogeton ftuitans 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'-13' long, 2"-12" wide, rounded at the base or tapering into a petiole l'-4' long; stipules 1'-4' 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, 1" - 1 1/2" 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 inside of the base.

In ponds and slow streams, New Brunswick to Washington, Florida, West Indies, and California. July-Oct.

8. Potamogeton Faxoni Morong. Faxon's Pondweed

Fig. 181

Potamogeton Faxoni Morong, Mem. Torr. Club, 3: Part 2, 22. 1893.

Floating leaves numerous, mostly obovate or oblanceolate, blunt-pointed or obtuse at the apex, narrowed at the base, often strikingly like those of P. varians, 2'- 3 1/2' long, 8"-12" wide, 13-17-nerved, on petioles 2'-6' long; submerged leaves oblong-lanceolate, acute or sometimes obtuse, 3'-5' long, 6"-12" wide, 5-13-nerved, often with an irregular areolation on each side of the midrib, borne on petioles ¥-2' in length; peduncles slightly thicker than the stem, 2'-5' long; spikes dense, 1'-2' long; fruit not collected.

Little Otter Creek and Lake Champlain, Ferris-burg, Vermont.

9. Potamogeton Heterophyllus Schreb. Various-Leaved Pondweed

Fig. 182

Potamogeton heterophyllus Schreb. Spicil. Fl.

Lips. 21. 1771. Potamogeton heterophyllus var. maximus Morong, Mem. Torr. Club, 3: Part 2, 25. 1893. Potamogeton heterophyllus var. longipendunculatus Morong, Mem. Torr. Club, 3: Part 2, 24.

1893. Potamogeton heterophyllus graminifolius Morong.

Mem. Torr. Club, 3: Part 2, 24. 1893. Potamogeton heterophyllus myriophyllus Morong,

Mem. Torr. Club, 3: Part 2, 24. 1893. Potamogeton heterophyllus minimus Morong,

Mem. Torr. Club, 3: Part 2, 25. 1893.

Stems slender, compressed, much branched, sometimes 12º long. Floating leaves pointed at the apex, rounded or subcordate at the base, 8"-4' long, 4"-14" wide, 10-18-nerved, on petioles 1'-4' long; submerged leaves pellucid, sessile, linear or linear-lanceolate, acuminate or cuspidate, rather stiff or flaccid, 1'-6 1/2 long, 1"-8" wide, 3-7-nerved, the uppermost often petioled; peduncles often thickened upward, 1'-7' long, sometimes clustered; stipules spreading, obtuse, 8"-12" long; spikes 9'-1 1/4' long; fruit roundish or obliquely obovoid, 1"-1 1/2" long, 1/2" - 1" thick, indistinctly 3-keeled; style short, obtuse, apical; apex of the embryo nearly touching the base, pointing slightly inside of it.

A very variable species, occurring in different forms throughout almost all North America except the extreme north. Also in Europe. July-Sept.