74 



NAIADACEAE. 



23. Potamogeton Friesii Ruprecht. Fries' Pondweed. (Fig. 164.) 



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



pi. 418. 1794- Not L. I753- 

 Potamogeton pit sill us var. major Fnes, Novit. Ed. 2, 



48. 1828. 

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



4: 43. 1845. 



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

 2,41. 1893. Not/". pnsillns\ar. major yi. 6t K. 1823, 

 Stems compressed, 2-4 long, branching. Leaves 

 i/^'-z^' long, about i" wide, acute, obtuse or cus- 

 pidate at the apex, mostly 5-nerved, rarely y-nerved, 

 2-glandular at the base, the glands small ; stipules 

 white, hyaline, finely nerved, obtuse or acute, 6"- 

 12" long; peduncles I'-i^' long, often thicker 

 than the stem and sometimes thickening upward; 

 spikes, when developed, interrupted; fruit quite sim- 

 ilar to that of P. pusillus, 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. Also in Europe. Propagating buds 

 occasional. July-Aug. 



24. Potamogeton rutilus Wolfg. Slender Pondweed. (Fig. 165.) 



Potaniogelon rutiltis Wolfg. ; R. &S. Mant. 3:362. 1827. 



Stems very slender, 8 / -24 / long, compressed, sim- 

 ple or nearly so. Leaves \'-\ l / 2 ' long, W~W 

 wide, acute or acuminate, strict, nearly erect, 3-5- 

 uerved, revolute, 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 %" thkk, 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 Vaseyi Robbins in A. Gray, Man. Ed. 5, 



485. 1867. 

 Potamogeton Vasevi var. la/ifolms Moroiig, Mem. 



Torr. Club, 3: Part 2, 44. 1893. 



Stems filiform, widely branching below, and with 

 many short lateral branches above, i-l i ^long, the 

 emersed fertile forms in shallow water, and the more 

 common sterile submerged forms in water frorn6- 

 8 in depth. Floating leaves on the fertile steins 

 only, coriaceous, in 1-4 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 // loug ; submerged leaves 

 capillary, I'-iJ^' 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 i" 

 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. 



