Glossary
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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
Image Credit: Loren Bahls
Image Credit: Loren Bahls
Image Credit: Loren Bahls
Figure 1. This diatom has a total of 21 striae.
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.