Phylum: Charophyta   Family: Desmidiaceae

Staurastrum manfeldtii var. parvum E. Messikommer 1942

This small variety of S. manfeldtii is not well known but has the characteristic rounded, swollen, base to the semicells. It needs to be compared with S. crenulatum sensu G.S. West 1899 – however, this deviates considerably from Nägeli’s (1849: 129, pl. 8: B) original description and illustrations as Phycastrum crenulatum and would perhaps be better renamed. Messikommer's original finds were all 4-radiate but triradiate forms would appear to be commoner. The processes are parallel or slightly divergent. The granulation, especially at the base of the semicells, can be quite pronounced to seemingly lacking.
Cell dimensions: L: 24-30 µm; B: 39-42 µm; Is: 6-8.5 µm; L/B: 0.6-0.7.
A seemingly rare taxon in the Outer Hebrides but possibly overlooked or misidentified in the past. The habitat is slightly acidic, mesotrophic waters such as shallow vegetated pools and loch-margins.

References: 
Van Westen, M.C. (2024). Sieralgen in Drenthe.