Central tube

Fultoportulae Int
Image Credit: Marina Potapova
Internal view of valve of Stephanodiscus sp. (SEM) showing the rimoportula (R), central fultoportula (CF) and four marginal fultoportulae (MF). Each fultoportula has two satellite pores surrounding the central tube.
Stephanodiscus Fultoportula
Internal view of valve of Stephanodiscus sp. (SEM) showing several fultoportula (one with an arrow). The central pore of the fultoportulae is difficult to distinguish in this image.