Phylum: Charophyta   Family: Closteriaceae

Closterium juncidum J. Ralfs 1848

First described and illustrated by Ralfs (1848: 172, p. 29: 6). What used to be forma robustius, has now been subsumed into the nominate. It was noted for the striae being widely spaced, but this is now regarded as natural variation. This species has a considerable size range and earlier authors describe the longer cells as var. elongatum, and the smaller cells as var. brevius. Later analysis has shown no clear dividing line between them so the varieties are no longer recognised.
Cell dimensions: L: 180-500 µm; B: 8-12 µm; Ap: 3.0-5.0 µm; L/B: 18-50.
Relatively common in acidic conditions such as Sphagnum bogs.

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.
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1.