Phylum: Charophyta   Family: Desmidiaceae

Cosmarium vexatiforme  F.A.C. Kouwets 2025

This taxon has been raised to species level from C. vexatum var. lacustre Messikommer 1935. C. vexatum is regarded as a doubtful species.
Cell dimensions: L: 31.4-35.8 µm; B: 29.2-31.8 µm; Is: 10.3-12.2 µm; Th: 17.3-20.6 µm; L/B: 1.03-1.14.
Probably not scarce in suitable habitats. It prefers circumneutral waters and has been found with moss on wet rocks and from a flooded disused quarry.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.
Van Westen, M.C. (2024). Sieralgen in Drenthe.