Phylum: Charophyta Family: Desmidiaceae
Staurastrum gracile J. Ralfs 1848
A widespread species but easily confused with the very similar Staurastrum boreale. Found in slightly acidic, mesotrophic waters such as shallow vegetated pools and loch-margins. The only known zygospores are by Homfeld (1929) with 9-10 projections in face view (6–7 in S. boreale), and is larger.
References:
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Homfeld, H. (1929) Beitrag zur Kenntnis der Desmidiaceen Nordwestdeutschlands besonders ihrer Zygoten.