Potamogeton gramineus, L. Potamogeton alpinus, Balbis

6. P. gramineus L. View in CoL , Sp. Pl. 127 (1753) View Cited Treatment .

Floating leaves (if present) up to 7 x 3 cm, elliptical or ovate-elliptical, cuneate or rounded at the base, opaque; petiole often longerthan the lamina. Submergedleaves (at least the lower) up to 8 x 3 cm, sessile, narrowly elliptic-oblong to narrowly elliptical or oblanceolateoblong, cuneate at the base, acute or acuminate, minutely denticulate at least when young, with regularly ascending secondary veins (occasional leaves more or less reduced to phyllodes). Stipules conspicuous, herbaceous. Peduncles thickened upwards. Fruitlets 2-3 mm. 2« = 52. Much of Europe, but rare in the Mediterranean region. Au Be Br Bu?Co Cz Da Fa Fe Ga Ge Hb He Ho Hs Hu Is It Ju Lu No Po Rm Rs (N, B, C, W, E) Su Tu.

P. xnitens Weber , Suppl. Fl. Holsat. 5 (1787) (6 x 9) is a frequent and widespread hybrid which often closely resembles 6.

7. P. alpinus Balbis View in CoL , Mém. Acad. Sci. (Turin) 10-11 (Phys. Math. 1): 329 (1804).

Plant often tinged with red. Floating leaves (if present) up to 8 x 2 cm, elliptical to oblanceolate, cuneate at the base, opaque; petiole shorter than the lamina. Submerged leaves up to 15 x 2 cm, sessile, lanceolate or linearlanceolate to elliptic-oblong, cuneate to rounded at the base and sometimes slightly amplexicaul, rounded or obtuse at the apex, entire; secondary veins mostly horizontal. Stipules large and conspicuous. Fruitlets 2-5- 3 mm, with a sharp dorsal keel. 2« = 26, 52. Much of Europe, but rare in the south. Au Be Br?Bu?CoCzDaFaFeGaGeGrHbHeHoHsIsItJuNoPoRm Rs (N, B, C, W, E) Su.