An alternately produced form of certain cryptogamous
   plants, as ferns, mosses, and the like, which bears antheridia and
   archegonia, and so has sexual fructification, as contrasted with the
   sporophore, which is nonsexual, but produces spores in countless
   number. In ferns the oophore is a minute prothallus; in mosses it is
   the leafy plant.