Phylum: Charophyta   Family: Desmidiaceae

Cosmarium blyttii var. novae-sylvae West & G.S. West 1897

Widespread in Britain in vegetated margins of lochs and bogs and seems to be well represented in the Outer Hebrides. It differs from the nominate in being slightly larger and has a variable mix of granules between the isthmus and the central granules

References: 
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands