GENUS i. 



PONDWEED FAMILY. 



23. Potamogeton Friesii Ruprecht. Fries' 

 Pondvveed. Fig. 196. 



Potamogeton compresses J. E. Smith, Engl. Bot. 3 : 



pi. 418. 1794. Not L. 1753. 

 Potamogeton pttsillus var. major Fries, Novit. Ed. 2, 



48. 1828. 

 Potamogeton Friesii Ruprecht, Beitr. Pfl. Russ. Reichs, 



4: 43. 1845. 

 Potamogeton major Morong, Mem. Torr. Club, 3 : Part 



2, 41. 1893. Not P. pusillus var. major M. & K. 1823. 



Stems compressed, 2-4 long, branching. Leaves 

 ii'-2i' long, about i" wide, acute, obtuse or cuspi- 

 date 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"-i2" 

 long; peduncles i'-ij' long, often thicker than the 

 stem and sometimes thickening upward ; spikes, when 

 developed, interrupted ; fruit quite similar to that of 

 P. pusillns, 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 

 North Dakota and Iowa. Also in Europe. Propagating buds occasional. July-Aug. 



24. Potamogeton rutilus Wolfg. Slender 

 Pondweed. Fig. 197. 



Potamogeton rutilus Wolfg. ; R. & S. Mant. 3 : 362. 1827. 



Stems very slender, 8'-24' long, compressed, simple 

 or nearly so. Leaves i'-i' long, i"-$" wide, acute 

 or acuminate, strict, nearly erect, 3-s-nerved, revo- 

 lute, the nerves prominent beneath, often 2-glandular 

 at base and bright green ; stipules acute, 6"-io" long, 

 often longer than the internodes and hiding the bases 

 of the leaves above, persistent, becoming white and 

 fibrous with age* peduncles 6"-i8" long; spikes 3"-5" 

 long, usually dense, but sometimes interrupted; fruit 

 obliquely obovoid, about i" long and 4" thick, ob- 

 scurely 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 complete, the apex pointing towards or outside 

 the base. 



Anticosti and James Bay to Michigan and Minnesota, 

 south to New York. Also in Europe. Propagating 

 buds usually wanting. 



25. Potamogeton Vaseyi Robbins. Vasey's 

 Pondweed. Fig. 198. 



Potamogeton Vaseyi Robbing in A. Gray, Man. Ed. 5, 



485. 1867. 

 Potamogeton Vaseyi var. latifolius Morong, Mem. Torr. 



Club, 3: Part 2. 44. 1893. 



Stems filiform, widely branching below, and with 

 many short lateral branches above, i-ii 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 1-4 opposite pairs, oval oblong or 

 obovate, 4"-5" long, 2"-$" wide, with 5-9 nerves 

 deeply impressed beneath, tapering at the base into 

 petioles 3"-4" long ; submerged leaves capillary, i'-ii' 

 long; stipules white, delicate, many-nerved, acute or 

 obtuse, 2"-3_" long; peduncles 3 "-6" long, thickening 

 in fruit ; spikes 2 '-3 'Jong, 2-6-f ruited ; fruit round- 

 ish-obovoid, about i" long and nearly as thick, 

 3-keeled, the middle keel rounded, tipped with a 

 straight or recurved style. 



Quebec to Wisconsin, south to southern New York. 

 The plant is furnished with propagating buds. July-Aug. 



