Phylum: Charophyta   Family: Desmidiaceae

Staurastrum vestitum J. Ralfs 1848

A medium-sized cell with an open sinus. Semicells subfusiform with the apex slightly convex with about six emarginate granules. There are two subapical bifurcate spines. The processes are parallel to slightly convergent with about four spines at the tips. Ralfs (l.c.) describes them as ‘minute’, but they vary considerably between populations. In apical view the two subapical bifurcate spines show prominently. West, West & Carter (1023: 158) give overall dimensions of LxB: 28-43 x 46-90 µm, whereas Ralfs (1848: 143) dimensions (calculated from inches) are LxB: 40 x 60 µm, perhaps more realistic for this nominate variety.
Overall cell dimensions: L: 33-43 µm; B: 51-61 µm; Is: 11.6-13.5 µm, L/B: 0.66-0.70.
Found in slightly acidic habitats such as in the plankton of lochs, especially at altitude. It’s infrequently recorded in the Outer Hebrides.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Ralfs, J. (1848). The British Desmidieae.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.