Phylum: Charophyta   Family: Desmidiaceae

Cosmarium polygonum var. depressum Messikommer

This rather small cell is currently regarded as rare but is easily overlooked and perhaps misidentified. It was first found by Messikommer (1942) in the Swiss Alps. Its habitat preference is not clearly defined but circumneutral to acidic in oligotrophic waters would fit current finds.

References: 
Messikommer, E. (1942) Beitrag zur Kenntnis der Algenflora und Algenvegetation des Hochgebirges um Davos
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium