Phylum: Charophyta   Family: Desmidiaceae

Cosmocladium saxonicum A. de Bary 1865

Colonies are free-floating and can have a large number of cells. Cells are connected by microfibrils that are secreted from pores at the base of the semicells. The largest of the British species.
Cell dimensions: L: 21-27 µm; B: 17-20 µm; Is: 5-7.5 µm; Th: 11-14 µm.
West, West & Carter (1923: 202) specifically mention Harris in the Outer Hebrides as one of the sites where the species has been found. A rare species, found in nutrient-poor waters such as acidic lochs.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.