Phylum: Charophyta   Family: Desmidiaceae

Docidium baculum J. Ralfs 1848

First published in Ralfs (1848: 158, pl. 33) after a description by Brébisson. West & West (1904: 193) recorded for Scotland: “Widely distributed but scarce ... not uncommon in the Outer Hebrides.”
Cell dimensions: L: 200-300 µm; B: 11-16 µm; L/B: 15-25.
Found in acidic moorland pools, lochans and disused peat-cuttings. West & West (l.c.: 194) go on to say: “Although this is the most frequent British species of the genus, it is nevertheless somewhat rare.”

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ralfs, J. (1848) The British Desmidieae.
Ruzicka, J. (1977) Die Desmidiaceen Mitteleuropas, Volume 1, Part 1.
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1.