266 FLUVIALES. [Potamogeton. 



7. P. perfoliatus, Linn. Perfoliate Pond-weed. Leaves 

 cordato-ovate, amplexicaul, 7-nerved, with smaller intermediate 

 nerves. Br. Fl 1. p. 74. E. FL u. i. p. 229. E. Bot. t. 

 168. 



t Ditches and lakes, in many places. FL July. If. Leaves pellu- 

 cid, olive-coloured. Peduncles rather short, thick. Spikes raised 

 above the water, consisting of a few brownish flowers, with white 

 pollen. 



8. P. lucens, Linn. Shining Pond-weed. Leaves elliptic- 

 Janceolate, mucronate, with several opposite pairs of parallel 

 nerves springing from the midrib, connected by reticulations ; 

 spike cylindrical, many-flowered. Br. Fl. i. p. 75. E. Fl.v. i. 

 p. 231. E. Bot. t. 376. 



Lake?, pools, and streams not unfrequent. FL June, July. It. 

 A large species, very beautiful in the nervation of its leaves, which are 

 of an olive-green colour. Spikes raised above the water, with nu- 

 merous green flowers. 



9. P. prtdonguS) Wulff. Long stalked Pond-weed. Leaves 

 oblong, obtuse, with three principal and several linear parallel 

 nerves arising from the base, connected by reticulations ; pe- 

 duncles elongated ; spikes cylindrical, many-flowered. Br. Fl. 

 cd. 3. p. 77. 



In one of the small lakes above Kilrea, County of Derry ; Mr. D. 

 Moore. FL June, Juty. 1. " This is best distinguished by its truly 

 oblong (by no means elliptical) leaves, nerved from the base, where 

 they are semiamplexical, and by the lengthened peduncle. In size it 

 almost equals P. lucens. Reichenbach has given an excellent repre- 

 sentation of this species." Hooker. 



$ $ $ $ HC Leaves alternate, upper ones floating, broader than 

 the rest ; stipules free. 



10. P. JieteropJiyllus, Schreb. Various-leaved Pond-weed. 

 Upper leaves elliptical, stalked, floating, slightly coriaceous ; 

 lower ones lanceolate, membranaceous, sessile ; flowerstalks 

 swelling upwards. Br. FL 1. p. 75. E. Bot. t. 1285. E. Fl. v. i. 

 p. 229. 



Rivers and lakes. In the river Liffey, above the Salmon-leap. 

 River Lee, above the basin, and at Sunday's-well ; Mr. J. Drum- 

 mond. River Bann, between three and four feet long, and flowering, 

 without any floating leaves ; Mr. D. Moore. FL June, July. 1. 

 Leaves distantly inserted on the stem, upper ones considerably larger 

 than the rest. " Distinguished by these marks from P. rufescens and 

 P. lanceolatus" Wilson. 



11. P. rufescens, Schrad. Reddish Pond-weed. Submersed 

 leaves lanceolate, membranaceous, . many-nerved, with con- 

 necting veins, and many linear reticulations at the midrib ; 

 floating ones subcoriacrous, on long stalks. Br. FL 1. p. 75. 

 P.fluitans, E. Bot. t. 128-3. E. FL v. i. p 230. (not of Roth.) 



