Formations of smaller pondweeds, in particular, Potamogeton crispus, Potamogeton filiformis, Potamogeton pusillus, Potamogeton obtusifolius, Potamogeton berchtoldii, Potamogeton trichoides, Potamogeton acutifolius, Potamogeton pectinatus, Potamogeton nitens, Potamogeton friesii (Potamogeton mucronatus), Groenlandia densa, waterthymes and waterweeds (Elodea spp., Hydrilla spp., Ottelia spp.), horned pondweeds (Zannichellia palustris s.l.), naiads (Najas spp.), tapegrass (Vallisneria spiralis), water crowfoots (Ranunculus circinatus) that colonize shallower, more sheltered Palaearctic waters. Eurasian formations dominated by usually free-floating hornworts of genus Ceratophyllum, in particular by Ceratophyllum demersum, are included because of closer ecological and physiognomic similarity with communities of this unit than with those of unit C1.32.