Beschreibung:
The paper presents comparative analysis of habitats of 19 phytocoenoses of the <em>Nymphaeetum candidae </em>and 21 phytocoenoses of the <em>Nupharo-Nymphaeetum albae </em>dominated by <em>N. alba </em>from the lakes of north-eastern Poland. The differences in ecological amplitudes and optima of occurence between two phytocoenose types were pronounced. The <em>N. candida </em>phytocoenoses had narrower amplitudes both regarding the properties of water and substrate and required higher minimum nutrient contents as compared to the <em>N. alba </em>phytocoenoses. Habitat distinction of phytocoenoses dominated by <em>N. candida </em>expressed in a relatively narrow trophic amplitude totally justifies to distinguish <em>Nymphaeetum candidae </em>as a separate syntaxon.