NAIADACEAE. 43 



slightly impressed; embryo circle incomplete, the apex pointing toward the base. 

 In still water, Anticosti to N. Penn. and N. J. Summer. 



3. Potamogeton amplifolius Tuckerm. Large-leaved Pondweed. (I. 



F. f. 144.) Stems long, simple or occasionally branched. Floating leaves oval or 

 ovate, abruptly pointed at the apex, rounded at the base, 5-10 cm. long, 3-5 cm. 

 wide, many-nerved ; submerged leaves mostly petioled, large, the uppermost often 

 elliptic or oval, 7-15 cm. long, 2-5 cm. wide, the lowest lanceolate, often 20 cm. 

 long, with about 25 nerves, often with the sides closed and assuming a falcate shape; 

 stipules tapering to a long sharp point, sometimes 10 cm. long ; peduncles thickened 

 upward, 5-20 cm. long; spikes 2-5 cm. long; fruit 4-5 mm. long, 2.5 mm. thick, 

 turgid, the pericarp hard, obliquely obovoid, 3-keeled ; face more or less angled ; 

 style subapical ; embryo slightly incurved. In lakes, Ont. to Br. Col., south to 

 Conn., Ky. and Neb. July-Sept. 



4. Potamogeton pulcher Tuckerm. Spotted Pondweed. (I. F. f. 145.) 

 Stems simple, terete, black-spotted, 0.3-0.7 mm. long. Floating leaves usually 

 massed at the top on short lateral branches, alternate, ovate or round-ovate, sub- 

 cordate, 2-8 cm. long, 5-1 1 cm. wide, many-nerved; peduncles about as thick as 

 the stem, 5-10 cm. long, spotted ; submerged leaves of 2 kinds, the uppermost 

 pellucid, lanceolate, long-acuminate, undulate, 7-20 cm. long, I-3.5 cm. wide, 

 tapering at the base into a short petiole, 10-20-nerved ; the lowest much thicker, 

 opaque, spatulate, long; stipules 2-carinate ; fruit 4-4.5 mm. long, 3 mm. thick, 

 turgid, tapering into a stout apical style, the back sharply 3-keeled ; face angled 

 near the middle, with a sinus below ; embryo coiled. In ponds and pools, Me. to 

 Ga. and Mo. July. 



5. Potamogeton Nuttallii Cham. & Sch. Nuttall's Pondweed. (I. F. f. 

 146.) Stems slender, compressed, mostly simple, 0.3-2 m. long. Floating leaves 

 opposite, elliptic, to obovate, obtuse, short-petioled, 3-8 cm. long, 8-24 mm. wide, 

 many-nerved; submerged leaves linear, 2-ranked, 5— 17 cm. long, 2-6 mm. wide, 

 5-nerved, the 2 outer nerves nearly marginal, the space between the 2 inner and 

 the midrib reticulated ; stipules obtuse, hyaline, not keeled ; peduncles 2-1 3 cm. 

 long; spikes 1-2.5 cm. long; fruit round-obovoid 2.5-4 mm. long, 2-3 mm. thick, 

 3-keeled, the sides fiat and indistinctly impressed ; style short, apical ; embryo 

 coiled one and one-third times. In ponds and streams, N. S. to Penn. and S. C. 

 June-Aug. (/>. Claytonii Tuckerm.) 



6. Potamogeton alpinus Balbis. Northern Pondweed. (I. F. f. 147.) 

 Plant of a ruddy tinge; stems simple or branched, somewhat compressed. Float- 

 ing leaves spatulate or oblanceolate, obtuse, many -nerved, tapering into petioles 

 2-12 cm. long; submerged leaves semi-pellucid, the lowest sessile, the uppermost 

 petioled, oblong-linear or linear-lanceolate, obtuse or rarely acute, narrowed at the 

 base, 7-30 cm. long, 4-20 mm. wide. 7-17-nerved; stipules broad, faintly 2-cari- 

 nate, obtuse or rarely acute; spikes 2-3 cm. long; fruit obovoid, lenticular, reddish, 

 2 5 mm. long, 2 mm. thick, 3-keeled. the middle keel sharp, the face arched, 

 beaked by the short recurved style ; apex of the embryo pointing directly to the 

 basal end. In ponds. N. S. to Br. Col., N. J. and Cal. Also in Europe. 

 July- Aug. {P. rufescens Schrad.) 



7. Potamogeton lonchites Tuckerm. Long-leaved Pondweed. (I. F. f. 

 148.) Stem terete, much branched, 1-2 m. long. Floating leaves rather thin, 

 elliptic, pointed at both ends, 5-15 cm. long, 1-3 cm. wide, many - nerved, 

 petioled; submerged leaves pellucid, 10-32 cm. long, 4-24 mm. wide, rounded at 

 the base or tapering into a petiole; stipules acuminate, strongly or faintly 2- 

 carinate; peduncles thickening upward, 5-8 cm. long; spikes cylindric, 2-5 cm. 

 long; fruit about 4 mm. long. 2-3 mm. 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, N. Br. to Wash., 

 Fla. and CaL July-Oct 



Potamogeton lonchites Noveboracensis Morong. Floating- leaves thicker, 7-14 cm. 

 long, about 5 cm. wide, 20-24-nerved, abruptly pointed or obtuse at the apex ; peduncles 

 60metiro.es 10-12 cm. and spikes 7.5 cm. long. Lakes of Cent. X. Y. 



8. Potamogeton Faxoni Morong. Faxon's Pondweed. (I. F. f. 149.) 

 Floating leaves numerous, mostly obovate or oblanceolate, blunt-pointed or obtuse 



