Phylum: Charophyta   Family: Desmidiaceae

Cosmarium hexalobum f. longum E.K. Kosinskaya

Kosinskaya (1933 from Russia) was the first to describe these longer and narrower cells of the nominate as forma longum. There have been a number since which have been provisionally corralled under this forma. Both the nominate and formae are rare arctic-alpine species.

References: 
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium