Diatoms of North AmericaDiatoms of North America

Glossary

Like the rest of this website, the glossary is a work in progress. If we’ve missed a term, please contact us to let us know the term and references.

Stria density and count in centric diatoms

Stria density is based on the number of striae in an arc of circumference. The density = total number of striae on the valve * 10 / circumference. In Figure 1, the stria density is equal to (21) (10) / 54.3 µm, or 3.9 striae in 10 µm of circumference.

Stria count is based on the number of striae in a chord of the valve face. In Figure 2, the chord crosses 5 striae, giving a count of 5 in 10 µm.

Citations

Centric Total
Image Credit: Loren Bahls
Figure 1. This diatom has a total of 21 striae.
Centric Chord
Image Credit: Loren Bahls
Figure 2. The red line shows a 10 µm chord. It crosses 5 striae, giving a stria count of 5 in 10 µm.
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