Collum
A structure found in the genus Aulacoseira. The collum is the narrow, hyaline area on the valve mantle. A small furrow, the sulcus, separates the collum from the portion of the valve mantle with areolae.
Citations
Barber, H.G. and Hayworth, E.Y. (1981). Guide to the Morphology of the Diatom Frustule. Freshwater Biological Association, 112 pp.
Image Credit: Marina Potapova
Each arrow shows the collum on two valves of a single frustule in *A. alpigena".
Image Credit: Marina Potapova
Each arrow shows the collum on two valves within a single frustule in A. humilis.
Image Credit: Marina Potapova
A single valve of A. nivalis, showing the collum.