?IoI –NPi SPi Pe StE EC NC NE ?NAe ?WAe ?Kik –KK ?EAe
Greece (East Aegean islands ‒ doubtfully present; East Central Greece ‒ present; Ionian Islands ‒ doubtfully present; Kiklades ‒ doubtfully present; Kriti and Karpathos ‒ absent; North Aegean islands ‒ doubtfully present; North Central Greece ‒ present; North Pindos ‒ absent; North-East Greece ‒ present; Peloponnisos ‒ present; South Pindos ‒ present; Sterea Ellas ‒ present; West Aegean islands ‒ doubtfully present)
Freshwater habitats, Coastal habitats
Island records from the Ionian and Aegean Seas are solely based on material revised by, or determined on advice of J. Zieliński who advocates the controversial synonymisation of T. parviflora with T. tetrandra; they are all likely to refer to T. parviflora if the two species are kept separate (Th. Raus).