Cell of C. perforatum. Notice the broad cell isthmus (shallow sinus), papillate basal angles and pronounced cell wall pores.
Cell dimensions (L x B): 60 x 55 µm
C. perforatum is a rather large-sized, smooth-walled Cosmarium species that can readily be recognized by its shallow, acute-angled, open cell sinus. In frontal view, semicells are about semicircular with a truncate apex and papillate basal angles. In its name, the epitheton 'perforatum' refers to pronounced cell wall pores rendering the wall a perforated appearance. In the Netherlands, C. perforatum is a very rare species, not encountered since more than half a century.
Image © Henk Schulp (after Czech material)
Another cell of C. perforatum (showing a more vital chloroplast).
SEM image © Jan Šťastný
SEM picture of C. perforatum. Notice marked cell wall scrobicles in centre of the semicell.