GENUS i. 



PONDWEED FAMILY. 



81 



17. Potamogetcn confervoides Reichb. Alga-like Pond weed. Fig. 190. 



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



13. 1845. 



Potamogcton 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'-2i' long, the broadest scarcely i" wide, taper- 

 ing to a long hair-like point, i-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"-il" 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 1 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, 

 i'-4' long, 3"-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 i'-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 il" long, i" 

 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 zosteraefolius Schum. Enum. PI. Saell. 50. 

 1801. 



Stems much flattened, sometimes winged, widely 

 branching. Leaves linear, obtuse and mucronate or 

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

 3 principal nerves and many fine ones ; stipules scarious, 

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

 long; spikes cylindric, about i' long, 12-15-flowered; 

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

 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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