256 NAJADACEiE. Potamogeton. 



5. Potamogeton perfoliatus, Linn. Perfoliate Pondweed. 



Stem somewliat branched ; leaves all submersed, oblong-ovate, obtuse, somewhat cordate 

 at the base, sessile and clasping, membranaceous and pellucid, a little rough on the margin ; 

 spikes oblong, few-flowered ; fruit slightly keeled. — Linn. sp. I. p. 126 ; Michx. fl. 2. p. 101 ; 

 Pursh, fl. 1. p. 120 ; Torr. fl. \. p. \Q1 ; Bigel. fl. Bost. p. 63 ; Cham. ^ Schlecht. I. c. 

 p. 188. t. 5. f. 13 ; Beck, hot. p. 386 ; Darlingt. fl. Cest. p. 115 ; Hook. fl. Bor'.-Am. 2. 

 p. 172; Ku7ith, syn. 3. p. 133. 



Stem slender, dichotomously branched. Leaves usually about an inch long, sometimes 

 ovate-lanceolate and acute, slightly waved on the margin, obscurely marked with 5 — 7 larger 

 and several intermediate nerves. Stipules membranaceous and pellucid like the leaves, often 

 wanting. Peduncles stout, about an inch long. Fruit obliquely ovale, the sides compressed ; 

 the seed uncinately curved. 



Ponds and streams : common. Fl. August. Fr. September. 



*♦* Leaves all submersed and linear. 



6. Potamogeton zosterifolius, Schumach. Grass-leaved Pondweed. 



Stem flatly compressed, branching ; leaves all linear and grass-like, pellucid, with three 

 primary and many smaller nerves, acuminate ; spikes cylindrical, on longish thick peduncles. 

 — Cham. 4- Schlecht. I. c. p. 182. t. 4. /. 10; Hook. fl. Bor.-Am. 2. p. 172 ; Kunth, enum. 

 3. p. 134. P. compressum, Torr. fl. 1. p. 198. P. acutifolium, H. H. Eat. in Trans, 

 journ. med. March, 1832, not of Link. P. Robbinsii, Oakes in Hovey^s mag. May, 1841? 



Stem almost winged, 2-4 feet long. Leaves 3-6 inches long and a line and a half or 

 2 lines wide, with a small abrupt acumination, marked with 3 pretty strong nerves besides 

 many much finer ones, but with very obscure connecting veins. Stipules free. Spike 6-9 

 lines long, on short peduncles which vary from 1-2 inches in length. Fruit obovate, some- 

 what lenticular, apiculate at the summit ; the keel obtuse. 



In the Hudson river above the Highlands, and in the western part of the State. Fl. August. 

 Fr. September. 



7. Potamogeton pusillus, Linn. Small Pondtoeed. 



Stem somewhat compressed ; leaves narrowly linear, 3 - 5-nerved, with distant and obscure 

 connecting veins, rather obtuse, pellucid ; spikes oblong, few-flowered, somewhat interrupted, 

 much shorter than the peduncles. — Linn. sp. I. p. 121 \ Cham. <J- Schlecht. I. c. p. 170. t.A. 

 f. 5 ; Kunth, enum. 3. p. 136. 



Stem branching, slender, flexuous. Leaves 1-2 inches long, about a line and a half wide, 

 mostly 5-nerved. Stipules membranaceous, large, obtuse, with a minute callosity or gland at 

 the base on each side. Spikes about half an inch long, mostly 6-flowered. Peduncles an 

 inch or more in length, thicker than the stem. " Fruit elliptical, oblique, the sides convex, 

 apiculate, with a very short style : keel obtuse." Cham. <^ Schlecht. 



