230 TETRANDRIA— TETRAGYNIA. Potamogetoii. 



Perennial. July, August. 



Whole plant immersed in the water, except the spikes, which con- 

 sist of a few brown flowers, with copious white pollen. Their 

 stalks are rather tumid in the upper part. Leaves all sessile, 

 1^ or 2 inches long, uniform, olive-coloured, pellucid like oiled 

 paper, as Haller remarks ; harsh to the touch, but brittle ; their 

 ribs reddish. Seeds compressed, shining. Stipulas tight and 

 close. 



Haller esteems Loesel's plant a distinct species, and it is his own 

 n. 844. Dillenius has introduced it into Ray's Synopsis, next 

 to P. perfoliatum. The leaves are said by Haller to be firm {dura) 

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

 lected near Berne, without^ou;ers, and the plant was never ob- 

 served afterwards. 



4. P. dens7im. Close-leaved Pond-weed. 



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

 Spike of four flowers. 



P. densum. Linn.Sp. Pl.\d,2. Willd.v.\.7\A. Fl.Br.\9A. Engl. 

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



P. n. 849. Hall. Hist. i!. 1.376. 



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

 149. 



Tribulus aquaticus minor 2. Clus. Hist. v. 2. 2.52. 



T. aquat. minor, muscatellae 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. Flowerstalks solitary, from the forks 

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

 flowers, 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. 1 . 72. v. 2. p. 1. 202. Willd. Sp. PI. v. 1 . 



713. Fl. Br. \39\. Engl. Bot. v. IS. t. 1286. Hook. Scot. 57. 



Fl.Dan. t. 1450? 

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

 Fontinalis lucens major. Bauh. Hist. i.o. 769./. 



