Zannichellia palustris, L.

1. Z. palustris L. , Sp. Pl. 969 (1753)

(incl. Z. major (Hartman) Boenn. ex Reichenb. , Z. pedunculata Reichenb. , Z. pedicellata (Wahlenb. & Rosén) Fries ).

Leaves up to 2 mm wide but usually narrower, subopposite (or alternate on non-flowering branches), acute, entire, sheaths free from the leaf-base, stipuliform, tubular when young, membranous, evanescent. Stamens 1-2. Carpels 2-9 (usually 4); stigmas peltate, with an irregularly crenate margin. Fruitlets 3-6 mm, stipitate or subsessile, laterally compressed, often curved, crenate-dentate, beaked. 2n= 12, 24, 28, 32, 34, 36. Still, fresh or brackish water. Almost throughout Europe. All except Al Az Fa Sb. Very variable in some flower- and fruit-characters, but not vegetatively. The male flowers may consist of one (2-thecous) anther or of two united anthers simulating a single 4-thecous anther. In the female flowers there is variation in the number of carpels and the shape of the stigmas, also in the degree of stipita- tion, the beak-length and the dentition of the fruitlets. Because of this many supposed taxa have been described at specific and infraspecific levels, and have been arranged in various conflicting ways, none of which appears satisfactory. The plants are here regarded as forming a single variable species.