Abstract
With the beginning of cyst formation plugs are formed in Acetabularia at the base of each cap ray. Precursor material of a granular-fibrillar structure is discharged from small vacuoles into the central vacuole of the stalk and accumulates in the coronae, while the secondary nuclei and the mass of the cytoplasm migrate into the cap rays. In the coronae the plug precursor forms fibrous, dense sponge-like obstructions. Structure and composition of the material differ significantly from that in Bryopsis hypnoides, which is chemically similar to that of Caulerpa simpliciuscula.