Phylum: Chlorophyta   Family: Oedogoniacea

Oedogonium platygynum V.B. Wittrock ex K.E. Hirn 1900

First described and illustrated by Wittrock in Hirn (1900: 276, pl. 47: 301). Later, Hirn (l.c.: 202, pl. 33: 207) regarded it as synonymous with Oedogonium itzigsohnii De Bary. This is surprising as it’s quite a bit smaller than O. itzigsohnii, apparently without overlap. John et al. (2011: 518, pl. 124H) has retained it as originally described. Capitellate cells are a significant feature of this species.
Dimensions: cells: L: 35-60 x B: 5-11 µm. Oogonia: L: 13-20 x B: 21-30 µm; Oospores: D: 13-24 µm.
Found in moorland pools and disused peat-cuttings. Infrequently recorded in the Outer Hebrides but likely to be overlooked.

References: 
Hirn, K.E. (1900). Monographie und iconographie der Oedogoniaceen.
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.