Phylum: Charophyta   Family: Closteriaceae

Closterium leibleinii var. boergesenii (Schmidle) Y.V. Roll 1915

Brook & Williamson (2010: pp. 293-296, pl. 139: 1-10) (for the nominate variety) describe it as cosmopolitan, occurring most frequently neutral to quite markedly alkaline waters (pH 6.5-8.5). In the Outer Hebrides it would seem that the nominate and var. boergesenii are rare.

References: 
Roll, Y.V. (1915) Matériaux pour servir à l'étude des algue de la Russie. Genus Closterium Nitzsch.
Brook, A.J. & Williamson, D.B. (2010) A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands.