Annulae

Annulae are groups of striae specific to the genus Geissleria. Annulae have one to four transapical striae that interrupt the typical striae on each side of the distal raphe ends. These striae may have areolae that are larger, more elongate, and more densely spaced. Internally in some species, these areolae possess a cluster of silica outgrowths. Annulae may be distinct or barely discernible, depending on the species. For example, the annulae of G. acceptata are difficult to resolve in LM.

Citations

Krammer, K. and Lange-Bertalot, H. (2000) Bacillariophyceae 5. English and French translation of the keys. In: Büdel, B., Gärtner, G., Krienitz, L. & Lokhorst, G. M. (eds.). Süßwasserflora von Mitteleuropa. 2(5), 311 pp. Spektrum Akademischer Verlag, Heidelberg-Berlin
Kulikovskiy, M., Andreeva, S., Gusev, E. and Annenkova, N. (2014) Phylogenetic position of the diatom genus Geissleria Lange-Bertalot & Metzeltin and description of two new species from Siberian mountain lakes Phytotaxa 177(5): 249-260

Publication Link: 10.11646/phytotaxa.177.5.1

Annulae — The annulae in this *Geissleria* are distinctive.

Internal view of *Geissleria cascadensis* (SEM). Annulae formed by three striae on either side of the distal end of the raphe. The areolae are covered by silica outgrowths. Scale bar = 2 µm.