MUTATIONAL LOAD IN A FERN POPULATION GROWING IN A POLLUTED ENVIRONMENT

The Osmunda regalis sporophyte is well organized for the storage and perpetuation of post‐zygotic mutations. Techniques have been developed to detect sporophytes in which such mutations have occurred. Two populations were screened for sporophytes which are chimeras for gametophytic or recessive sporophytic lethals. The populations had different ecologies; one was in a pristine lake side bog and the other was growing in the waters of a river heavily polluted with industrial wastes. Post‐zygotic mutations were detected only in the polluted river population. The level of mutational damage approximated that previously documented from chromosome studies.