one of the minute grains in flowerless plants, which are analogous to seeds, as serving to reproduce the species.-an embryo sac or embryonal vesicle in the ovules of flowering plants.-a minute grain or germ; a small, round or ovoid body, formed in certain organisms, and by germination giving rise to a new organism; as, the reproductive spores of bacteria, etc.-one of the parts formed by fission in certain protozoa. see spore formation, belw.