Phylum: Charophyta   Family: Closteriaceae

Closterium cornu  J. Ralfs 1848

A slender desmid, similar to Closterium upsaliense but larger. The apices are often thickened and usually have a single, quite large terminal granule.
Cell dimensions: L. 100-158 µm; B. 10-11.2 µm; Ap: 2.8-3.4 µm; L/B. 10-15.
Found in acidic to mildly alkaline waters such as moorland pools and ditches.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe.