Polymorphism in the desmid Cosmarium taxichondrum Lundell

Polymorphism in a population of C. taxichondrum Lundell var. taxichondrum has been studied. Cell outline does not vary greatly but variability in the morphology of the basal angles shows that var. bidentulum Lagerheim must be reduced to synonymy with var. taxichondrum. The subapical set of granules, usually 5 or 6, may be reduced to three or be completely lacking. The central set of granules exhibits great variability (3–7) and may even occasionally be lacking. Large isthmus granules are usually present, but their usefulness in separating C. taxichondrum and C. pseudotaxichondrum Nordst. is questioned.