Phylum: Charophyta   Family: Mesotaeniaceae

Mesotaenium endlicherianum C. Nägeli 1849

First described and illustrated by Nägeli (1849: 108, pl. 6: B). Brook & Williamson (2010: 85) note: “The cells are frequently filled with food reserves, which may completely obscure the chloroplast (l.c., pl. 35: 11).” Several authors give a varying range of sizes; the broadest cells are perhaps better described as var. grande.
Cell dimensions: L: 22-44 µm; B: 7-11 µm, L/B: 2.3-4.2.
Typical habitat would be acidic moorland pools and bogs. This type of habitat is common in the Outer Hebrides but this taxon is proving elusive. West & West (1904: 56) note: "This species sometimes occurs in quantity in boggy pools or at the boggy margins of mountain lakes and tarns."

References: 
Brook, A.J. & Williamson, D.B. (2010) A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Nägeli, C. (1849) Gattungen einzelliger Algen, physiologisch und systematisch bearbeitet.
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1.