817 Ceratophyllum demersum L.

This species is extremely widespread, not only in Eurasia and N. America. Same lower taxa are distinguished in different parts of the world, in Europe at least two (Fl. Eur. 1/1964, p. 206). The characteristic fruits are often found in postglacial layers outside the area of common occurrence (for Fennoscandia see Hultén, Atlas 1971, map 771). The occurrences outside the map area are noted peripherically. The species belongs to the circumpolar plants (Hultén, Circumpol. Il, p. 116 and map 107).