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Guide to Planothidium frequentissimum

(Lange-Bert. in Krammer and Lange-Bert.) Lange-Bert. 1999

Planothidium Frequentissimum2 Guide
Credit: Marina Potapova
  1. Valves lanceolate to elliptic, with rounded or slightly drawn-out apices
  2. Valves 3-6 μm wide
  3. Rapheless valve with a cavum

Valves are lanceolate to elliptic with rounded or slightly drawn-out apices, 5-17 μm long and 3-6 μm wide. The rapheless valve has a linear-lanceolate axial area that slightly widens in the middle. The central area contains a cavum on the internal valve surface.