228 TETRANDRIA— TETRAGYNIA. Polamogeton. 

 81. POTAMOGETON. Pond-weed. 



Linn. Gen. 67. Juss.]9. Fl. Br. \93. Br. Pr. 343. Tour n. t. 103. 

 Lam. t. 89. Gcertn. t. 84. 



Nat. Ord. InundatcE. Linn. 15. Naiades. Juss. 6. Alisma- 

 cecE. DeCand. 116. Br. Pr. 342. N. 82 the same. 



Cal. none. Cov. inferior, of 4 roundish, obtuse, concave, 

 equal, incurved petals^ with cla'isos about their own length, 

 deciduous. Filam. flat, very short, often more than 4. 

 Anth. exterior, oblong, 2-Iobed. Germens 4, superior, 

 ovate, acute, gibbous. Styles generally none. Stigm. ob- 

 tuse, permanent. Seeds 4, naked, roundish ; tumid at the 

 back ; compressed or angular at the inner margin. ''Em- 

 bryo curved," almost double. Gcsrt?i. Br, 



Aquatic, floating or immersed, herbs, of a highly vascular 

 texture, whose evaporation, by their whole surface, is ex- 

 tremely copious and rapid. Stem branched. Leaves alter- 

 nate, or opposite, stalked or sessile, simple, undivided, 

 entire, rather membranous, smooth, with parallel longitu- 

 dinal ribs. Flowet's spiked, greenish, raised above the 

 water; the seeds ripened at the bottom. Four of our 

 species are found in New Holland. 



1. P. natans. Broad-leaved Pond-weed. 



Upper leaves oblong-ovate, stalked, floating, coriaceous ; 

 lower ones linear, membranous, sessile. 



P. natans. Linn. Sp. PL 182. fVilld. v. 1. 712. Fl. Br. 193. Engl. 



Bot. V. 26. t. 1822. Hook. Scot. 57. Mill. Illustr. MI. Fl. Dan. 



t. 102.5. Br. Prodr. 343. 

 P. n. 843. Hall. Hist. v. 1. 375. 

 P. rotundifolium. Raii Syn. 148. Bauh. Pin. 193. 

 P. latifolium. Ger. Em. 821./. 

 Potamogeton. Matth. Valgr. v. 2. 481./. Camer. Epit. 873. /. 



Fuchs. Hist. 651. f. Trag. Hist. 688. /. 



In pools, ditches, and slow rivers. 



Perennial. July. 



Roots creeping extensively in the mud. Stem round, much branch- 

 ed, several feet in length. Lowermost leaves alternate, linear, 

 acute, very narrow, sessile, membranous ; uppermost floating, 

 partly opposite, leathery, smooth, deep green, 2 or 3 inches long, 

 elliptical, often heart-shaped, with about 7 main ribs, and some 

 intermediate ones ; involute in the bud. Footstalks various in 

 length, semicylindrical, very vascular. Stipidas intrafoliaceous, 

 large, lanceolate, acute, concave, pale and membranous. Spikes 

 simple, raised an inch or two above the water, each on a long, 



