Callitriche palustris, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 125

9. C. palustris L. , Sp. Pl. 969 (1753)

(C. verna L. , C. vernalis Koch ).

Submerged leaves very narrowly linear; floating rosettes with elliptical or suborbicular leaves; in terrestrial form, leaves small, elliptical. Disc of cauline hairs orbicular, of 12-15 cells. Usually 1 male and 1 female flower in the same leaf-axil. Pollengrains subglobose. Styles erect, caducous. Fruit 1 (-1-5) mm, obovate, rarely elliptical, blackish; mericarps winged only at apex, the cells of the wing thickened on radial walls, not tapering. 2/2 = 20. Shallow, still water. Europe, southwards to the Pyrenees, Corse and the lower Volga, mainly in the mountains except in Fennoscandia & Russia. Au fBe Br Bu Co Cz Da Fe Ga Ge He Ho?Hs Hu Is It No Po Rm Rs (N, B, C, W,?K, E) Su.

In the terrestrial form, the male flowers and styles are reduced or absent.

Variants with almost elliptical fruits and scarcely winged mericarps occur in the Pyrenees, with fruits up to 1 -5 mm in E. Switzerland, and with broadly winged mericarps in E. Europe. Their status is uncertain.

(d) Three fruiting forms: submerged; aquatic with floating rosettes; and terrestrial. Submerged leaves not transparent. Disc of cauline hairs of (8-) 12-20 cells. Flowers solitary. Bracteoles 2, deciduous, or absent. Stamen recurved towards one of the deflexed styles; anther-wall with thin-walled cells; pollen-grains colourless, without exine. Wing of mericarp composed of a single row of short cells with thickening on the radial and proximal walls. Basic chromosome number?7.