Foricula

A foricula is a thin outgrowth of silica with a wide point of attachment partially occluding an areola. It is usually found on the outside of the valve and is a feature exclusive to the Cymbellales. From Latin for window shutter. Plural is foriculae.

Six shapes of slit openings are recognized in Cox (2004):
- unilateral (Gomphonema)
- symmetrical (many Cymbella sensu stricto)
- uneven (Cymbella deliculata and allies)
- round (Gomphoneis, Reimeria)
- tri- or quadriradiate (Cymbella ehrenbergii and allies)
- dendritic (Didymosphenia)

Citations

Cox, E.J. (2004) Pore occlusions in raphid diatoms - a reassessment of their structure and terminology, with particular reference to members of the Cymbellales. Diatom 20: 33-46.

Publication Link: 10.11464/diatom1985.20.0_33
Idei M., Sato S. and Mann D.G. (2020) The Amazing World of Diatoms. Sogensha Publishers, Osaka, Japan, pp. 176.