Elodea canadensis, Michx

1. E. canadensis Michx View in CoL , FI. Bor. Amer. 1: 20 (1803).

Leaves up to 17x4 mm but usually c. 10 x 2 mm, in whorls of 3 or the lowest opposite, usually oblong-linear, rounded at the apex, minutely denticulate, more or less crowded. Sepals of female flowers 2-2-7 mm; petals white or pale purple. 2« = 24, 48.

Lakes, rivers and canals; mainly in base-rich waters. Naturalized almost throughout Europe, except for the Arctic and most of the islands. [Au Be Br Bu Cz Da Fe Ga Ge Hb He Ho Hs Hu It Ju Lu No Po Rm Rs (N, B, C, W, E) Su.] (North America.)

First naturalized in Ireland in 1834, and on the continent in 1859. In most parts of Europe male plants are rare or absent.