Callitrichaceae
Plants aquatic or creeping on mud Callitrichaceae
Leaves rhomboidal, apiculate, usually with a tooth on either edge. Styles less than 1 mm long. Mature fruit broader than long, brown, with a pale wing one third the width of the mericarp. Widespread Callitriche muelleri
Leaves spathulate or ovate, blunt, not toothed. Styles 2–3 mm long. Mature fruit pale, not broader than long; the wing less than one third the width of the mericarp. Widespread. Introd. from N. hemisphere Callitriche stagnalis