Phylum: Charophyta   Family: Desmidiaceae

Cosmarium granatum Brébisson ex Ralfs 1848

A common, widespread species of differing habitats including Sphagnum bogs and less acidic loch-margins, moorland pools and ephemeral water-bodies. (The cells depicted below from the latter habitat are distorted suggesting a stressed emvironment.)

References: 
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland
West, W. & West, G.S. (1905) A Monograph of the British Desmidiaceae, Volume 2