Abstract
In the wild-type and B-mutant hyphae of S. commune, acid phosphatase activity was found in association with vacuoles, lipid bodies and endoplasmic reticulum. Small granules containing acid phosphatase also occurred in mitochondria and along the nuclear envelope. Ultrastructural and biochemical studies indicated greater acid phosphatase activity in the B-mutant than in the wild-type hyphae, which suggests that the mutation in the B incompatibility factor increases the production of the acid phosphatase in the mutant hyphae.