The earliest authenticated specimens of Marchantia polymorpha var. aquatica from Cheboygan County, Michigan, were collected by Margaret Fulford in 1951 at Iron Bridge, Carp Creek (UMBS). Campbell (1969), in her account of Marchantia in Michigan, gave further documentation of the Iron Bridge population, and we have had the locality under observation for an extended period of time (1968-1981) in order to determine the seasonal events enabling this colony to persist. These mechanisms maintain the populations in the pools, adding new plants produced from gemmae to the continuing growth of older thalli from the preceding year. Both suspended new and old thalli in the pools continue to grow through the spring and into the summer. These aspects account for the persistent population in the pools and also for downstream distribution. By late spring gemma production has ceased. It would appear that Marchantia polymorpha var. aquatica at Iron Bridge is an excellent example of asexual propagules playing a key role in the persistence of a liverwort population.