Glossary
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Polar bar
A polar bar is a hyaline thickening of silica at the valve apex in some pennate species. The genus Sellaphora possesses variable development of polar bars.
Alternative Terms
- transapical thickening
Some authors use "transapical thickening", rather than polar bar.
Image Credit: Marina Potapova
Image Credit: Marina Potapova
Image Credit: Marina Potapova
Scanning electron micrograph of Sellaphora wallacei showing the polar bar at the apex.
Image Credit: Marina Potapova
Light micrograph of Sellaphora rexii, with the thickening of the polar bar appearing lighter than other parts of the valve.