prothallium

In botany, a thalloid oöphyte or its homologue; a little thalloid structure resembling a lichen or Marchantia, which is produced by the germination of the spore in the higher cryptogams, and which bears the sexual organs (antheridia and archegonia).

Same as prothallus.

A plant, usually a pteridophyte, in gametophyte stage in the metagenesis cycle.

The young gametophyte of a liverwort or peat moss.