Phylum: Charophyta Family: Desmidiaceae
Cosmarium tatricum Raciborski 1885
An Arctic-alpine species which is rare in Britain and confined to the north and west. Associated with acidic boggy ground with often dense vegetation but also found with moss on wet rocks. It is very similar to Cosmarium decedens but has a smaller L/B ratio. The sides tend to narrow towards the apex in this species rather more than in Cosmarium decedens, but there are intermediate cells, which are confusing.
References:
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.
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3