Stria

A stria is a row of areolae, alveoli, or is a single alveolus when the alveolus extends from the apical axis to the margin. The 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. In Latin, stria means groove or stripe.

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.

Citations

Ross, R., Cox, E.J., Karayeva, N.I., Mann, D.G., Paddock, T.B.B., Simonsen, R. and Sims, P.A. (1979) An amended terminology for the siliceous components of the diatom cell Nova Hedwigia, Beihefte 64: 513-533
Round, F.E., Crawford, R.M. and Mann, D.G. (1990) The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Gomphoneis Geitleri Ex 1 — External view of *Gomphosinica geitleri* showing the multiseriate striae.

46104 Sem2 1 — External view of *Navicula tripunctata* showing the lineolate areolae composing the uniseriate striae.

A33 Sei 037 — External view of *Cavinula pseudoscutiformis* showing the uniseriate, radiate striae.