Phylum: Charophyta   Family: Desmidiaceae

Cosmarium septentrionaliforme F.A.C. Kouwets 2025

This recently described species is intended to clear up confusion over similar species. One of these C. septentrionale Croasdale 1973 sensu Coesel (1989) and Coesel & Meesters (2023). Interestingly, Van Westen (2024: 490 as C. septentrionale Croasdale 1973), notes “the cells found in Drenthe match the illustrations in those works, but the cells found here are smaller. It is quite possible that the cells found in Drenthe are a different, undescribed species.” – (Broadly translated). Kouwets (2025: 577) has provisionally included these dimensions in parentheses. The cells depicted here match the sizes of Van Westen’s.
Cell dimensions (3): L: 22.9-28.5 µm, B: 20.3-23.6 µm, Is: 6.6-8.5 µm; Th: c.15.3 µm, L/B: 1.11-1.21.
Because of taxonomic confusion and the disparity in cell dimensions, its status in the Outer Hebrides is unclear.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
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.