Phylum: Charophyta   Family: Desmidiaceae

Pleurotaenium trabecula var. crassum V.B. Wittrock 1872

This variety is broader and stockier than the nominate giving a smaller L/B ratio. The semicells are often swollen giving a broader dimension than the basal inflation. Occasionally a hint of a secondary inflation can be observed.
Cell dimensions: L: 240-450 µm; B: 30-48 µm; L/B: 6.5-10.5.
Much scarcer than the nominate variety. The few Outer Hebridean finds have come from slightly alkaline waters.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.