106 TETRANDRIA TETRAGYKIA. [ci*. IT. 



from our most severe winters. Flowers in May : grows in bushy 

 places : frequent. Eng. Bot. vol. vii. pi. 496. Eng. Fl. vol. i. p. 228. 



263. 



17. POTAMOGE'TON. POND-WEED. 



Calyx none. Corolla inferior, of four roundish equal petals, 

 furnished with a claw. Filaments very short, flat ; anthers ob- 

 long, two-lobed. Germens four, superior, egg-shaped, acute. 

 Style none ; stigmas obtuse, permanent. Seeds four, roundish, 

 bulging on one side, flattened on the other. Named from pota- 

 mosy a river, and geiton, a neighbour. 80. 



1. P. ndtans. Broad-leaved Pond-weed. Upper leaves between 

 oblong and egg-shaped, stalked, leathery, floating ; lower leaves 



linear, membranous, sessile. Stem round, much branched: upper 



leaves brownish-green : spikes simple, raised above the water : the 

 floating leaves afford an agreeable shade to fish, and the roots are a 

 favourite food of swans. Perennial : flowers in July and August : 

 grows in pools, ditches, canals, and rivers : common. Eng. Bot. 

 vol. xxvi. pi. 1822. Eng. Fl. vol. i. p. 229. 264. 



2. P.heterophyl'lus. Various-leaved Pond-weed. Upper leaves ellip- 

 tical, stalked, slightly leathery, floating; lower leaves lance- 

 shaped, membranous, sessile. Smaller than the last: upper 



leaves thinner : flower-stalks enlarged upwards : spikes dense. 

 Perennial : flowers in July and August : grows in pools, ditches, 

 canals, and rivers : common. Eng. Bot. vol. xviii. pi. 1285. Eng. 

 FL vol. i. p. 229. 265. 



3. P. rufescens. Long-leaved Floating Pond-weed. Upper leaves 

 between egg-shaped and lance- shaped, stalked, leathery, floating ; 



lower leaves lance- shaped, membranous, sessile. Upper leaves 



less leathery, olive-coloured or reddish. Perennial : flowers in July 

 and August : grows in ditches, ponds, and slow rivers. Eng. Bot. 

 vol. xviii. pi. 1286. Eng. FL vol. i. p. 231. P.fluitans. 266. 



4. P. perfolidtus. Perfoliate Pond-weed. Leaves heart-shaped, 



embracing the stem, uniform, all submersed. Leaves all sessile, 



uniform, very pellucid, olive -coloured. Perennial: flowers in July 

 and August : grows in slow rivers and ponds : common. Eng. Bqt. 

 vol. iii. pi. 168. Eng. FL vol. i. p. 230. 267. 



5. P. densus. Close-leaved Pond-weed. Leaves opposite, egg- 

 shaped, tapering to a point, crowded; stem forked; spike four- 

 flowered. Fruit-stalk very short, in the fork of the stem : all the 



leaves are submersed, and very close together. Perennial : flowers 

 in July and August : grows in ditches, ponds, and slow rivers : 

 common. Eng. Bot. vol. vi. pi. 397. Eng. Fl. vol. i. p. 231. 268. 



6. P. lucens. Shining Pond-weed. Leaves between elliptical and 

 lance-shaped, pointed, stalked, membranous, sessile; spike dense, 

 many-flowered. Leaves large, olive-green, with undulated mar- 

 gins, and beautifully veined : spike two inches long, of very nume- 

 rous, green flowers. Perennial : flowers in June and July : grows 

 in ditches, ponds, lakes, and slow rivers : common. Eng. Bot. vol. 

 vi. pi. 376. Eng. FL vol. i. p. 232. 269. 



7. P. prelongus. Long-stalked Pond-weed. Leaves oblong, ob- 

 tuse, sessile ; peduncles much elongated ; spike cylindrical, many- 



