Rimmed depression

A hyaline depression on the inside of a valve. It occurs only in some species of the genus Planothidium and is a depression of the asymmetrical central area on the rapheless valve. See also hood.

Alternative Terms

hufeisen
The German term used to describe this structure is also used in English floras.
Planothidum Ringed Dep
Image Credit: Marina Potapova
A scanning electron micrograph of the inside of the rapheless valve of a species of Planothidium. The arrow indicates the rimmed depression.
De000084 4
Image Credit: Marina Potapova
A light micrograph of the rapheless valve of a species of Planothidium with the rimmed depression at the arrow.