FO 
NAIADACEAE. 
11. Potamogeton Illinoénsis Morong. 
Illinois Pondweed. (Fig. 152.) 
Potamogeton Illinoensis Morong, Coult. Bot. Gaz. 
5:50. 1880 
Stem stout, much branched above. Floating 
leaves opposite, numerous, thick, 4’-5 14’ long, 
2/-314’ wide, many-nerved, oval or broadly ellip- 
tic, short-pointed at the apex, rounded, subcor- 
date or narrowed at the base; petioles 1/-4/ long; 
submerged leaves numerous, 4’-8’ long, 1/-2/ 
wide, 13-19-nerved, acuminate or the uppermost 
acute, mostly tapering at the base into a short 
broad flat petiole, rarely reduced to phyllodes; 
stipules 2/-3’ long, obtuse, strongly 2-carinate; 
peduncles 2’-4’ long; spikes 1/-2’ long; fruit 
roundish or obovoid, 114’’-2’’ long, 1//-114// 
thick, dorsally 3-kecled ; style short, blunt. 
In ponds, Illinois to Iowa and Minnesota. Aug. 
12. Potamogeton Zizii Roth. Ziz’s Pondweed. (Fig. 153.) 
Potamogeton angustifolius Berch. & Presl, Rost. 
1g. 1821. Not DC. 1805 
Potamogeton Zizii Roth, Enum. f: 531. 
Stems slender, branching. Floating leaves 
elliptic, 1144/-4’ long, 6//-12’’ wide, many- 
nerved; petioles mostly short; submerged 
leaves mostly lanceolate or oblanceolate, thin, 
acute or cuspidate, 2’-6’ long, 3/’-15’’ wide, 
7-17-nerved; stipules 6//-18’’ long, obtuse, 
2-keeled; peduncles thicker than the stem, 
2%4/-6’ long; spikes 1/-2’ long; fruit obliquely 
obovoid, 1% ’/-2’ long, about 1/’ thick, the face 
dorsally 3-keeled; style short, blunt, facial; apex 
of the embryo pointing directly to the base. 
In lakes and streams, Quebec to Montana, south to 
Floridaand Wyoming. Alsoin Europe. July—Aug. 
Potamogeton Zizii Methyénsis (A. Benn.) Morong. 
Potamogeton angustifolius var. Methyensis A. Ben- 
nett, Britten’s Journ. Bot. 29: 151. I89I. | 
Middle leaves narrow; upper leaves oval; stipules 
long; fruit small. Methy Lake, Canada. 
13. Potamogeton lucens L. Shining 
Pondweed. (Fig. 154. 
Potamogeton lucens \,. Sp. Pl. 126. 1753. 
Stem thick, branching below and often with 
masses of short leafy branches at the summit. 
Leaves all submerged, elliptic, lanceolate or the 
uppermost oval, shining, acute or acuminate and 
cuspidate, or rounded at both ends and merely 
mucronulate, sessile or short-petioled, 214/-8’ 
long, 8’’-20’’ wide, the tips often serrulate; 
stipules 1’-3’ long, 2-carinate, sometimes very 
broad; peduncles 3/-6’ long; spikes 2/24’ 
long, cylindric, very thick; fruit about 114’ 
long and 14’ thick, roundish, the face usually 
with a slight inward curve at the base; apex 
of the embryo pointing transversely inward. 
In ponds, Nova Scotia to Florida, west to Califor- 
niaand Mexico. Local. Alsoin Europe. Sept.—Oct. 
Potamogeton licens Connecticuténsis Robbins in A. Gray, Man. Ed. 5, 488. 1867. 
Stems flexuous; leaves acuminate; fruit larger than that of the type (about 2’’ long), distinctly 
3-carinate and with a facial style. Saltonstall’s Pond, Conn., and White Plains, N. Y. 
