Gametophyte, in plants and certain algae, the sexual phase (or an individual representing the phase) in the alternation of generations—a phenomenon in which two distinct phases occur in the life history of the organism, each phase producing the other. The nonsexual phase is the sporophyte.
Gametophyte generation of fern is called prothallus.
A pollination tube, or pollen tube, is a thin tube that is a part of the male gametophype. It is found in seed plants and works by acting as a sort of conduit to transport gamete cells.