摘要：The periderm of Orthograptus gracilis has bee studied with an electron microscope (TEM and SEM). Four components have been recognized within the thecal wall: 1. endocortex,2. fusellar layer,3. cortex and so-called 4. taeniocortex. Taeniocortex covering the outer surface of the thecal wall consists of ribbon or sometimes roller-like elements and is produced of a peculiar material. The data obtained do not confirm Andres' belief that ribbons are made of cortical material and that entire cortex was produced by deposition of ribbon-like units.
