C-Fern antheridiogen, the pheromone which determines the sexual phenotype of gametophytes, can be easily harvested and used in experiments. Use old cultures of gametophytes, preferably those which are not contaminated, and carefully scrape the gametophytes from the surface. Next, freeze and then thaw the agar. The liquid will separate from the agar and it can be autoclaved or microwaved and used in new cultures to influence development. Try a dose response!