Diatoms of North AmericaDiatoms of North America
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Guide to Stauroforma

Flower, Jones and Round 1996

Stauroforma Guide
  1. Valves lack rimoportulae
  2. Striae meet in central valve face
  3. Central area absent

Frustules of Stauroforma are small, with an elliptic to lanceolate valve outline. The valves not centrally expanded. Rimoportulae are absent in species of Stauroforma. The striae are continuous across the valve face, although this feature may be difficult to resolve in the light microscope. Frustules are linked together into linear colonies. Spines may be present or absent.

Stauroforma is composed of species formerly considered within Fragilaria virescens. Stauroforma lacks rimoportulae, which distinguishes it from Fragilariforma.