Myriophyllum verticillatum, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1981, Flora Europaea. Volume 2. Rosaceae to Umbelliferae, Cambridge University Press : 312

1. M. verticillatum L. , Sp. Pl. 992 (1753).

Stems up to 300 cm; perennation by davate turions. Leaves 25-45 mm, (4-)5(-6) in a whorl, often longer than internodes; segments 24-35. Spike 7-25 cm. Flowers usually in whorls of 5; bracts pinnatisect, 1-15 times as long as the flowers. A few hermaphrodite flowers usually present between male and female flowers. Petals 2-5 mm in male flowers, absent in female. Stamens 8. Fruit c. 3 mm, subglobose, smooth. 2« = 28. Almost throughout Europe. All except Az Co Cr Fa Sb. In the terrestrial state this species may be as small as 3 cm, with leaves 1 cm and with as few as 4 leaf-segments.