TETRANDRIA— TETRAGYNIA. Potamogeton. 231 



like those of the first ; but he had seen only a dry specimen col- 

 lected near Berne, without Jlowers, and the plant was never ob- 

 served afterwards. 



4. P. denswn. Close-leaved Pond-weed. 



Leaves ovate, pointed, opposite, crowded. Stem forked. 

 Spike of four flowers. 



P. densum. Linn. Sp. PL 182. Willd.v.\.7\4. Fl.Br. \94. Engl. 

 Bot. v. 6. t. 397. Hook. Scot. 58. Fl. Dan. t. 1264. 



P. n. 849. Hall. Hist. v. 1.376. 



P. seu Fontalis media lucens. Bauh. Hist. v. 3. 769./. Ran Syn. 

 149. 



Tribulus aquaticus minor 2. Clus. Hist. v. 2. 252. 



T. aquat. minor, muscatellse floribus. Goodyer in Ger. Em. 823 ; 

 but the figure is P. crispum. 



In ditches, ponds and slow streams, not uncommon. 



Perennial. June. 



Smaller than the last, and of a much brighter green. All the leaves 

 are under water, somewhat recurved, an inch or inch and half 

 long, very near together. Flower-stalks solitary, from the forks 

 of the stem, each bearing a small quadrangular head of 4 green 

 Jlowers, well compared, by Clusius and Goodyer, to the flowers 

 of Adoxa Moschatellina. This head is just out of the water du- 

 ring impregnation ; after which, by the increase of the branches, 

 it sinks, and ripens seed, whilst other flowers come forth above. 

 The deeper the water, the larger is the whole plant. 



5. V.fluitans. Long-leaved Floating Pond-weed. 

 Lower leaves lanceolate, pointed and membranous, with 



distinct ribs ; upper elliptic-oblong, stalked, coriaceous, 

 obtuse, floating. 



P. fluitans. Roth Germ.v.\. 72. v.2.p.l. 202. Wild. Sp. PL v. 1 . 

 713. Fl. Br. 1391. Engl. Bot. v. 18. 1. 1286. Hook. Scot. 57. 

 Fl.Dan.t. 1450? 



P. n. 847. Hall. Hist. v. 1 . 376 ; excl. the syn. of Limiceus. 



Fontinalis lucens major. Bauh. Hist. v. 3. 769./. 



In ponds, ditches, and slow streams. 



In ditches, in marshy ground near Beverley, Yorkshire. Mr. Tees- 

 dale. Lilleshall mill-pool, Shropshire. Rev. E. Williams. In 

 the river at Scole, Norfolk. Mr. Woodward and Mr. D. Turner. 



Perennial. July, August. . . • *i 



As large as the first species, with which it agrees in having the 

 upper leaves floating, and considerably coriaceous ; but it is 

 really more akin to lucens, from which Haller had much diffi- 

 culty to distinguish our plant. He speaks of it as very com- 

 mon in Switzerland, and 1 have many specimens from the tate 



