Phylum: Charophyta   Family: Desmidiaceae

Cosmarium laeviforme F.A.C. Kouwets 2025

Rabenhorst's original description (Cosmarium laeve Rabenhorst 1868) is rather brief and sketchy and lacks a drawing, which has led to confused interpretations and spawned many varieties. Kouwets (2025) has taken the better-known populations and renamed them here.
Single cell dimensions: L: 27.3 µm; B: 19 µm; Is: 5.2 µm; Th: 13.2 µm; L/B: 1.44.
Found in circumneutral to more acidic habitats. Because of earlier taxonomic confusion, the status in the Outer Hebrides is unknown but seemingly scarce.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.