Phylum: Charophyta   Family: Closteriaceae

Closterium subscoticum morpha 

This cell has all the feature of Cl. subscoticum but differs in two noticeable ways: firstly it is slightly broader than the accepted upper limit of 12.5 µm, and secondly the end sections attenuate more sharply. It has all the usual features of Cl. subscoticum such as fine striae, truncate-rounded apices, which are slightly swollen (capitate), with a single crystal. It is probably just an aberrant form.
Cell dimensions: L: 312 µm; B: 14.8 µm; Ap: 6.8; L/B: 21.
Cl. subscoticum is a rare species found in slightly to more pronounced acidic condition such as peaty pools, bogs and loch-margins. This supposedly aberrant form was found with a good population of Cl. subscoticum. Interestingly, Brook & Williamson (2010: 233 for Cl. subscoticum) note: “… usually associated with Sphagnum.” I have never found it with Sphagnum.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.