Ophiolgossum pusillum, the northern adder's-tongue (Ophioglossaceae), is a small, inconspicuous fern of wetlands and moist meadows. Once common throughout the northeastern U.S., it has declined dramatically in recent decades. Historical records exist from 90 Massachusetts towns, yet today it is known from only seven localities in the state. It is listed as endangered or threatened in MA and in a number of other states. This study sought to relocate historical records in Massachusetts, examine the population biology of extant populations, and make management recommendations. Five populations were located in summer 1991. Starch gel electrophoresis revealed no genetic variation in plants from four Massachusetts populations. One New Hampshire population showed possible variation. Low variability may be a result of the reproductive biology of the species which readily self-fertilizes and expands vegetatively. While low genetic variability may explain the decline of the species, habitat loss is a clear factor in some sites. In fact, genetic variability may not be as important in this early successional species as the ability to spread rapidly and disperse to new habitat as conditions change.

Key words: Massachusetts, Northern adder's-tongue fern, Ophioglossum pusillum, population biology