NAIAD ACE AE. 



Potamogeton confervoides Reichb. Alga-like Pondweed. (Fig. 158.) 



Potamogeton conferi'oides 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'-2>'long, the broadest scarcely 

 W wide, tapering to a long hair-like point, 1-3 -nerved 

 and often with a few cross-veins, bright green or yellow- 

 ish ; stipules delicate, obtuse, 2 // ~3 // long; peduncles 2 / -8 r 

 long, erect, somewhat thickened upward ; spikes capitate, 

 3"-4"long; fruit roundish-obovoid, \"-\y z " long and 

 about as thick, the back sometimes a little angular or sin- 

 uate, 3-keeled, the middle keel sharp, the face notched 

 near the base, the sides impressed with a shallow indenta- 

 tion 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. Also in Europe. Aug. -Sept. 



18. Potamogeton crispus L. Curled-leaved Pondweed. (Fig. 159.) 



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, 

 yi'-tf long, z fr ~l" wide, 3~7-nerved, the midrib 

 often compound and the outer nerves very near the 

 margin ; stipules small, scarious, obtuse, early per- 

 ishing ; peduncles i'-2' long, frequently recurved 

 in fruit, sometimes very numerous ; spikes about 

 %' long, appearing very bristly with the long- 

 beaked drupelets when in fruit ; fruit ovoid, about 

 i}4" long, \" 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 propagated by peculiar winter buds. 



In fresh, brackish or even salt water, Massachusetts 

 to Pennsylvania and Virginia. Also in Europe. Aug. 



19. Potamogeton zosteraefolius Schum. Eel-grass Pondweed. (Fig. 1 60.) 



Potamogeton zosteraefolius Schum. Enum. PI. Saell. 50, 



1801. 

 Potamogeton compressus Fries, Novit. Ed. 2, 44. 1828. 



Not L. 1753- 



Stems much flattened, sometimes winged, widely 

 branching. Leaves linear, obtuse and mucronate or 

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

 3 principal nerves and many fine ones ; stipules scari- 

 ous, obtuse, finely nerved, soon perishing ; peduncles 

 i/4'-4' long; spikes cylindric, about %' long, 12-15- 

 flowered ; fruit obovoid with a broad base, about 2" 

 long, i X"-!^" 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 propagated by the terminal leaf-buds, which 

 sink to the bottom, and rest during the winter. 



In still or running water. New Brunswick to New Jer- 

 sey, west to Oregon. Also in Europe. July-Aug. 



