Actinotaenium species lacks ornamentation and are in most cases described on basis of their size and outline. Close examination revealed, however, that specimen with roughly the same shape and size may differ considerably in the distribution of the pores or pore fields across the cell surface and in the form of their chloroplasts. Especially if these properties are not mentioned in the original description, a number of taxa will constantly be under discussion and that will not stop until all these forms have been thoroughly examined, particularly with the use of scanning electron microscopy.

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