Phylum: Charophyta   Family: Desmidiaceae

Cosmarium subundulatum J.N.F. Wille 1881

First described and illustrated by Wille (1880: 27, pl. I: 9). A characteristic species with undulate sides and a slight notch in the apex.
Cell dimensions: L: 53-62 µm; B: 38-44 µm; Is: 17-20 µm; Th: 27-33 µm; L/B: 1.31-1.54.
Acidophilic from moorland pools and loch margins, also from abandoned peat-cuttings. Status uncertain for the Outer Hebrides but infrequently recorded.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Kouwets, F.A.C. (in manuscript). European Flora of the Desmid Genus Cosmarium.
Wille, N. (1880). Bidrag till Kundskaben om Norges Ferskvandsalger 1. Smaalenenes. Chlorophyllophyceer.