TETRANDRIA— TETRAGYNIA. Potamogeton. 299 



thick, axillary stalk, suddenly contracted at the bottom of the 

 spike. F/. a little distant, quite sessile, rather numerous, ver- 

 tical, olive green, with yellow anthers, and plenty of whitish 

 pollen. 

 Except as manure, I know of no use for this, or any of the genus. 



2. P. heterophyllum. Various-leaved Pond-weed. 

 Upper leaves elliptical, stalked, floating, slightly coriaceous; 



lower ones lanceolate, membranous, sessile. Flowerstalks 



swelling upward. 



P. heterophyllum . Schreh. Lips. 2 1 . mild. Sp. Pl.v.\.7\3. Hoffm 

 Germ, for 1800. 81. Fl. Br. 1390. Engl. Bot. v. 18. t. 1285. 

 Hook. Scot. 57. Hopk. Glott. 27. Fl. Dan. t. 1263. 



P. palustre. Teesdale Tr. of Linn. Soc. v. 5. 43. Relh. 64. 



P. gramineum. Lightf. 123. Fl. Dan. t. 222; without the floating 

 leaves. 



P. forte species, foliis tenuibus et pellucidis, lapathi minoris forma. 

 Dill, in Rail Syn. 150? 



P. folio angusto pellucido fere gramineo. Raii Syn. 148. ? 



P. n. 850. Hall. Hist. v. ].377; excluding the reference to Ray. 



In pools and ditches. 



Near Beverley, Yorkshire. Mr. Teesdale. Berrington pool, Shrop- 

 shire. Rev. E. Williams. Cambridgeshire. Relh. &; Rev. J. Hem- 

 sted. At Old Buckenham, Norfolk. Mr. D. Turner. In Bar- 

 dowie loch, Clydesdale. Hopkirk. Angusshire. Mr. G. Don. 



Perennial. July — September. 



Smaller than the last. Floating leaves thinner, generally more 

 pointed, scarcely heart-shaped, seldom 2 inches long^ the sub- 

 mersed ones excessively numerous, lanceolate, tapering at each 

 end, not linear ; their length 1| or 2 inches j breadth at most 

 half an inch ; with 3 or 5 principal ribs. Stipulas blunter and 

 shorter than the former. Flower-stalks swelling upwards, or club- 

 shaped, often crowded at the tops of the branches. Spikes dense, 

 about an inch long, the stalks contracted suddenly below them. 



3. V, perfoliatinn. Perfoliate Pond-weed. 



Leaves heart-shaped, clasping the stem, uniform, all sub- 

 mersed. 



P. perfoliatum. Linn. Sp. PI. 182. mild. v. 1. 713. Fl. Br. 104. 



Engl. Bot. V. 3. t. 108. Hook. Scot. 58. Fl. Dan. t. 196. Raii 



Syn. 149. Br. Prodr. 343. 

 P. n. 845. Hall. Hist. v. I. 376. 

 P. tertia. Dod. Pempt. 582. f Ger. Em. 822. /. Bauh. Hist. v. 3, 



770./. 

 P. rotundifolium alterum. Loes. Pruss. 205. t. 65. 



In ponds and rivers, very common, 



