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Diagnostic features

Tapering, sheathed heteropolar filaments attached to surfaces. Spherical or near-spherical heterocyte always occurs at the base of each filament. Basal cells often widened. Tufts formed by groups of filaments often trap sediment near the base. Filaments within groups are separated from each other (not in common mucilage), and false branching very rare to absent (cf. Dichothrix).

Typical habitats

Cold or geothermal waters.


Kingdom Bacteria
Phylum Cyanobacteria
Class Cyanophyceae
Order Nostocales
Family Rivulariaceae
Common name Cyanobacteria