Spondylosium secedens

Spondylosium secedens. June 2015, André Vanhoof found zygospores of a desmid species identified as Spondylosium secedens (de Bary) W.Archer 1861. The zygospores in question were globose and smooth-walled contrary to the spiny zygospores attributed to that species in Lütkemüller (1900) and copied in the well-known flora by West et al. (1923). Critical consideration of Lütkemüller's paper revealed that his figures of the vegetative cells of Spondylosium secedens should refer to another species than the one originally described by De Bary. So, likely, Spondylosium secedens is characterized by globose, smooth-walled zygospores, not by spiny ones. For that matter, it is questionable whether the Spondylosium species under discussion can be distinguished in a reliable way from given taxa in the genus Cosmarium.