Same as Prothallus.

In the reproductive cycle of ferns, a self-sustaining, independent plant, developing out of the growing spore. Green, heart shaped, ½" or less in diameter, and lying flat upon the ground it little resembles a fern, when noticed at all. The Prothallium grows Antheridia (male organs) and Archegonia (female organs) on its underside which produce the spermatazoids and eggs that combine and grow into what we think of as a fern. Also known as Gametophyte.

A prothallium, or prothallus; from Latin pro = forwards and Greek θαλλος (thallos) = twig; is usually a pteridophyte, i.e. spore-bearing plant, (almost exclusively ferns) in gametophyte stage in the alternation of generations cycle. Occasionally the term is also used to describe the young gametophyte of a liverwort or peat moss as well.

plural: Prothalla] the sexual generation of Pteridophyta.