74 NAIADACEAE. 
23. Potamogeton Friésii Ruprecht. Fries’ Pondweed. (Fig. 164.) 
Potamogeton compressus J. FE. Smith, Engl. Bot. 3: 
pl. g18. 1794. Not. 1753. 
Potamogeton pusillus var. major Fries, Novit. Ed. 2, 
48. 1828. 
Potamogeton Friesti Ruprecht, Beitr. Pfl. Russ. Reichs, 
4:43. 1845. : 
Potamogeton major Morong, Mem. Torr. Club, 3: Part 
2,41. 1893. Not P. pusi/lus var. major M. & K. 1823. 
Stems compressed, 2°-4° long, branching. Leaves 
114’-214’ long, about 1’ wide, acute, obtuse or cus- 
pidate at the apex, mostly 5-nerved, rarely 7-nerved, 
2-glandular at the base, the glands small; stipules 
white, hyaline, finely nerved, obtuse or acute, 6//— 
12’ long; peduncles 1/-114’ long, often thicker 
than the stem and sometimes thickening upward; 
spikes, when developed, interrupted; fruit quite sim- 
ilar to that of P. pusid/us, but with a recurved style, 
usually with a shallow pit on the sides, and with the 
apex of the embryo pointing toward the basal end. 
In still water, New Brunswick to New York, west to 
British Columbia. Alsoin Europe. Propagating buds 
occasional. July—Aug. 
24. Potamogeton rutilus Wolfg. Slender Pondweed. (Fig. 165. ) 
Potamogeton rutilus Wolfg.;R. & S. Mant. 3: 362. 1827. 
Stems very slender, 8/24’ long, compressed, sim- 
ple or nearly so. Leaves 1/-1'%4’ long, \%//-%4”” 
wide, acute or acuminate, strict, nearly erect, 3-5- 
neryed, revolute, the nerves prominent beneath, 
often 2-glandular at base and bright green ; stipules 
acute, 6’’-10’’ long, often longer than the internodes 
and hiding the bases of the leaves above, persistent, 
becoming white and fibrous with age; peduncles 
6/’-18” long; spikes 3/’-5’’ long, usually dense, but 
sometimes interrupted; fruit obliquely obovoid, 
about 1’ long and 14’ thick, obscurely keeled or 
the back showing only 2 small grooves; apex of 
the drupelet tapering into a short facial nearly 
straight recurved style; embryo circle not com- 
plete, the apex pointing a little inside of the base. 
Anticosti and James Bay to Michigan and Minnesota. 
Also in Europe. Propagating buds usually wanting. 
25. Potamogeton Vaseyi Robbins. Vasey’s Pondweed. (Fig. 166.) 
Potamogeton Waseyt Robbins in A. Gray, Man. Ed. 5, 
485. 1867. 
Potamogeton Waseyvit var. latifolins Morong, Mem. 
Torr. Club, 3: Part 2, 44. 1893. 
Stems filiform, widely branching below, and with 
many short lateral branches above, 1°-114° long, the 
emersed fertile forms in shallow water, and the more 
common sterile submerged forms in water from 6°— 
8° in depth. Floating leaves on the fertile stems 
only, coriaceous, in I-4 opposite pairs, oval oblong 
or obovate, 4/’-5’’ long, 2’’-3’’ wide, with 5-9 
nerves deeply impressed beneath, tapering at the 
base into petioles 3’’/-4’’ long; submerged leaves 
capillary, 1’-1'4’ long; stipules white, delicate, 
many-nerved, acute or obtuse, 2-3’ long; pedun- 
cles 3’’-6’’ long, thickening in fruit; spikes 2’’—3’’ 
long, 2-6-fruited ; fruit roundish-obovoid, about 1’” 
long and nearly as thick, 3-keeled, the middle keel 
rounded, tipped with a straight or recurved style. 
Eastern Massachusetts to southern Ontario and Ohio. 
The plant is furnished with propagative buds. July-Aug. 
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