Phylum: Charophyta   Family: Desmidiaceae

Cosmarium subtumidum var. groenbladii Croasdale

Differs from the nominate variety in that the semicells are rounded rectangular to hexagonal in outline - Coesel & Meesters (2007). It also has a slightly greater length/breadth ratio than the nominate

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