Euhydrophyte communities of Palaearctic streams poor in nutrients and in lime, with, in particular, Myriophyllum alterniflorum, Potamogeton polygonifolius, Callitriche hamulata, Littorella uniflora, Juncus bulbosus, Scirpus fluitans or acidophilous mosses and algae. In Iceland, Montia fontana, Potamogeton filiformis, Ranunculus trichophyllus (Ranunculus confervoides, Ranunculus aquatilis var. diffusus) and Fontinalis antipyretica characterize the community in clear, slowly flowing waters.