Phylum: Charophyta Family: Desmidiaceae
Euastrum binale Ehrenberg ex Ralfs
This nominate variety is rarely encountered even in suitable habitats. The Wests (1905) record it for Scotland as "General and abundant." and include the Outer Hebrides. Found in acidic, oligo-mesotrophic water.
References:
West, W. & West, G.S. (1905) A Monograph of the British Desmidiaceae, Volume 2
Ruzicka, J. (1981) Die Desmidiaceen Mitteleuropas, Volume 1, Part 2
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands