Stria

A stria is a row of areolae or alveoli. Latin for groove or stripe. Plural is striae.

In centric diatoms, striae are usually oriented along radii of a valve. In pennate diatoms, striae are usually oriented on the valve more or less transapically.

Features of the striae are important in diatom taxonomy and phylogeny, such as:
- density: number of striae that occur in 10 µm;
- orientation: radiate, parallel, or convergent;
- chambering: whether an alveolus or not;
- seriation: whether uni-, bi-, or multiseriate.

Gomphoneis Geitleri Ex 1
Image Credit: Marina Potapova
External view of Gomphosinica geitleri showing the multiseriate striae.
46104  Sem2 1
Image Credit: Marina Potapova
External view of Navicula tripunctata showing the lineolate areolae composing the uniseriate striae.
A33 Sei 037
Image Credit: Megan Otu
External view of Cavinula pseudoscutiformis showing the uniseriate, radiate striae.