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Guide to Planothidium delicatulum

(Kütz.) Round and Bukht. 1996

Planothidium Delicatulum Guide
Credit: Marina Potapova
  1. Apices protracted and subrostrate
  2. Raphe valve with transversely elliptical or rectangular central area
  3. Rapheless valve lacks a central area
  4. Rapheless valve may have 2 middle, distant striae on one valve side

Valves are lanceolate with protracted subrostrate apices. The raphe valve has a transversely elliptical or rectangular central area. The rapheless valve has a linear-lanceolate axial area and no distinguishable central area, or two middle striae on one side of the raphe can be slightly more distant for each other than from the other striae.