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Guide to Cocconeis placentula sensu lato

Ehrenb. 1838

Cocconeis Placentula Guide
Credit: Marina Potapova
  1. Valves relatively flat, elliptic to linear-elliptic
  2. Raphe valve with small central area
  3. Striae on raphe valve interrupted by hyaline ring
  4. Striae radiate

Valves are elliptic to linear-elliptic and relatively flat. The raphe valve has a narrow axial area and a small circular or oval central area. The raphe is straight and filiform. Striae are radiate in both raphe and rapheless valves. The striae on the raphe valve are interrupted by a hyaline ring positioned close to valve margin. Areolae are usually well distinguished under LM. The valvocopula attached to the raphe valve has conspicuous fimbriae. The rapheless valve has a linear to linear-lanceolate axial area.

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