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