Collum

A collum is the narrow, hyaline area at the edge of the valve mantle in the genus Aulacoseira.

The sulcus (a small furrow) separates the collum from the portion of the valve mantle with areolae.

See also ringleiste.

A Alpigena Collum
Image Credit: Marina Potapova
In this light micrograph, each arrow shows the collum on two valves of a single frustule in A. alpigena.
A Humilis Collum
Image Credit: Marina Potapova
In this scanning electron micrograph, each arrow shows the collum on two valves within a single frustule in A. humilis.
A Nivalis Collum
Image Credit: Marina Potapova
A scanning electron micrograph of a single valve of A. nivalis, showing the collum.