Hygronitrophilous plant communities of Pyrenaean Catalonia and its vicinities. The following communities have been recognized: Alliance Bidention tripartitae: Xanthio italici-Polygonetum persicarine O. Bolòs 1957, Bidentetum tripartitae W. Koch 1926 (= Polygono hydropiperis-Bidentetum tripartitae Lohm. in Tx. 1950) and Myosoto aquaticae-Bidentetum frondosae, ass. nova. Alliance Convolvulion sepium: Arundini-Convolvuletum sepium (Tx. and Oberd.) O. Bolòs 1962, Oenothero glaziovianae-Asteretum pilosi O. Bolòs and R. Masalles 1983 and Oenothero biennis-Helianthetum tuberosi, ass. nova.