Diatoms of North AmericaDiatoms of North America
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Compare Fragilariforma bicapitata

(A.Mayer) D.M.Williams and Round 1988

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Fragilariforma viriscens has a higher stria density and the valve is more lanceolate and less linear than F. bicapitata. Fragilariforma nitzschioides also has a higher stria density, but has distinctly linear valves across the entire size range.

LM scalebar = 10 µm
Fragilariforma bicapitata LM2 Fragilariforma bicapitata LM3 Fragilariforma bicapitata LM4 Fragilariforma bicapitata LM1 Fragilariforma bicapitata LM5 Fragilariforma bicapitata LM6 Fragilariforma bicapitata LM7
Length Range
9.1-51.1 µm
Width Range
2.9-5.5 µm
Striae in 10 µm
11-15

Fragilariforma virescens

(Ralfs) D.M.Williams and Round 1988

Fragilariforma virescens LM6 Fragilariforma virescens LM3 Fragilariforma virescens LM1 Fragilariforma virescens LM4 Fragilariforma virescens LM2 Fragilariforma virescens LM5
Length Range
15-60 µm
Width Range
6.5-7.0 µm
Striae in 10 µm
20-22

Fragilariforma nitzschioides

(Grunow) Lange-Bert. 2011

Fragilariforma nitzschioides LM3 Fragilariforma nitzschioides LM4 Fragilariforma nitzschioides LM5 Fragilariforma nitzschioides LM6 Fragilariforma nitzschioides LM2 Fragilariforma nitzschioides LM1 Fragilariforma nitzschioides LM7
Length Range
19-54 µm
Width Range
3.5-5.5 µm
Striae in 10 µm
18-25