an Entity references as follows:
Antheridiogens are a class of chemicals secreted by fern gametophytes that have "been shown to influence production of male gametangia and thus mating systems in a large number of terrestrial fern species". Antheridiogens are only observed in homosporous fern species, as all gametophytes are potentially bisexual (have the ability to produce both archegonia and antheridia).