A gametophyte is a haploid stage in the life cycle of plants and some algae, responsible for producing gametes (sperm and eggs) through mitosis. In the alternation of generations, the gametophyte develops from a spore and eventually fertilizes to form a diploid sporophyte. This stage is prominent in non-vascular plants like mosses, where the gametophyte is the dominant and most recognizable form. In vascular plants, the gametophyte is often reduced and dependent on the sporophyte for nourishment.