TETRANDRIA— TETRAGYNIA. Potamoffeton. 229 



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

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

 tical, olive gpreen, with yellove anthers, and plenty of whitish 

 pollen. 

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



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



Upper leaves elliptical, stalked, floating, slightly coriaceous; 

 lower ones lanceolate, membranous, sessile. Flowerstalks 

 swelling upward. 



P.heterophyllum. Schreb. Lips. 21. Willd. Sp.Pl.v.].7\3. Hoffm. 

 Germ, for J 800. 81 . Fl. Br. 1390. Engl. Bot. v. 1 8. t. 1285. 

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



P. palustre. Teesdale Tr. of Linn. Soc. v. 5. 43. Beth. 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. Ruii Syn. 148. ? 



P. n. 850. Hall. Hist. v. 1.377; excluding the reference to Ray. 



In pools and ditches. 



Near Beverley, Yorkshire. Mr. Teesdale. Berringtop 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. Jtihj — September. 



Smaller than the last. Floating leaves thinner, generally more * 

 pointed, scarcely heart-shaped, seldom 2 inches longj the sub- 

 mersed ones excessively numerous, lanceolate, tapering at each 

 end, not linear ; their length ]i or 2 inches ; breadth at most 

 half an inch ; witli 3 or 5 principal ribs. Sfipulas blunter and 

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

 shape;!, often crowded at the tops of the branches. Spikes dense, 

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



3. P. perfoliatum. 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. 194. 



Engl. Bot. V. 3. t. 168. Hook. Scot. 58. Fl. Dan. t. 196. Rail 



Syn. 149. Br. Prodr. 343. 

 P. n. 845. Hall. Hist. v. 1.376. 

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



770./. 

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



In ponds and rivers, very common. 



