Phylum: Chlorophyta   Family: Oedogoniacea

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

First described and illustrated by Wittrock in Hirn (1900: 83, pl. 2: 16). One of the smaller Oedogonium and can be locally common in suitable habitat. Like most Oedogonium, oogonia are necessary to identify to species.
Dimensions: cells: L: 44-75 x B: 12-14 µm. Oogonia: L: 34-42 x B: 37-46 µm; Oospores: D: 30-35 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.