Genus i. 



PONDWEED FAMILY. 



Si 



17. Potamogeton confervoides Reichb. Alga-like Pond weed. 



Potamogeton confervoides Reichb. Ic. Fl. Germ. & Helv. 7 : 



13- 1845. 

 Potamogeton trichoides A. Gray, Man. 457. 1848. Not Cham. 

 Potamogeton Tuckermani Robbins ; A. Gray, Man. Ed. 2, 434. 



1856. 



Stems slender, terete, much branched, the upper branches 

 repeatedly forking, 6'-i8' long. Leaves very delicate, flat, 

 setaceous, i'-24' long, the broadest scarcely i" wide, taper- 

 ing to a long hair-like point, 1-3-nerved and often with a 

 few cross-veins, bright green or yellowish; stipules deli- 

 cate, obtuse, 2"-3" long; peduncles 2'-8' long, erect, some- 

 what thickened upward ; spikes capitate, 3 "-4" long ; fruit 

 roundish-obovoid, i"-i4" long and about as thick, the back 

 sometimes a little angular or sinuate, 3-keeled, the middle 

 keel sharp, the face notched near the base, the sides im- 

 pressed with a shallow indentation which runs into the 

 notch of the face ; apex of the embryo nearly touching' the 

 base a little to one side. 



In cold or mountain ponds, Maine and New Hampshire to 

 New Jersey and Pennsylvania. Aug.-Sept. 



18. Potamogeton crispus L. Curly Muck-weed. Pondweed. Fig. 191. 



Potamogeton crispus L. Sp. PI. 126. 1753. 



Stems branching, compressed. Leaves 2-ranked, 

 linear-oblong or linear-oblanceolate, sessile or semi- 

 amplexicaul, obtuse at the apex, serrulate, crisped, 

 ¥-4' long, 2"~7" wide, 3-7-nerved, the midrib often 

 compound and the outer nerves very near the mar- 

 gin; stipules small, scarious, obtuse, early perishing; 

 peduncles 1/-2' long, frequently recurved in fruit, 

 sometimes very numerous ; spikes about ¥ long, 

 appearing very bristly with the long-beaked drupe- 

 lets when in fruit; fruit ovoid, about 1 4" long, 1" 

 or more wide, 3-keeled on the back, the middle keel 

 with a small projecting tooth near the base, the face 

 slightly curved, the style facial and nearly as long 

 as the drupelet ; embryo small, its apex pointing 

 directly toward its base. The plant is mainly propa- 

 gated by peculiar winter buds. 



In fresh or salt water, about cities, Massachusetts to 

 Pennsylvania and Virginia. Also in Europe. Aug. 



19. Potamogeton compressus L. Eel-grass 

 Pondweed. Fig. 192. 



Potamogeton compressus L. Sp. PI. 127. 1753. 

 Potamogeton sosteraefolius Schum. Enum. PI. Saell. 50. 

 1 801. 



Stems much flattened, sometimes winged, widely 

 branching. Leaves linear, obtuse and mucronate or 

 short-pointed at the apex, 2'-i2' long, i"-a" wide, with 

 3 principal nerves and many fine ones ; stipules scarious, 

 obtuse, finely nerved, soon perishing; peduncles ii'-4' 

 long; spikes cylindric, about ¥ long, 12-15-flowered; 

 fruit obovoid with a broad base, about 2" long, ii"-ii" 

 thick, 3-keeled on ■ the back, the lateral keels rather 

 obscure; face arched, beaked with a short recurved 

 style; embryo slightly incurved. The plant is propa- 

 gated by the terminal leaf-buds, which sink to the bot- 

 tom, and rest during the winter. 



In still or running water, New Brunswick to New York, 

 west to Oregon. Also in Europe. July-Aug. Grass-wrack. 



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