Axial plate

Internal 'plate' of silica that occludes the inner openings of the areolae. Found in some species of Gomphoneis where its margin appears as the longitudinal line that is visible in light microscopy.

Axial Plate Copy
Image Credit: Sarah Spaulding
Internal view of the central area of Gomphoneis herculeana showing the proximal raphe ends. The axial plate covers the internal expression of the areolae.
Image Credit: Pat Kociolek
The axial plate forms the longitudinal lines in Gomphoneis. Here the longitudinal lines are shown in G. herculeana.