Please see the refence

Page 302 of

York P V, Johnson L R. The freshwater algal flora of the British Isles: an identification guide to freshwater and terrestrial algae[M]. Cambridge University Press, 2002.

and

Van Vuuren S J, Taylor J, Gerber A, et al. Easy identification of the most common freshwater algae: a guide for the identification of microscopic algae in South African freshwaters[M]. Resource Quality Services (RQS), 2006.