(1):

(n.) An embryo sac or embryonal vesicle in the ovules of flowering plants.

(2):

(n.) One of the parts formed by fission in certain Protozoa. See Spore formation, belw.

(3):

(n.) One of the minute grains in flowerless plants, which are analogous to seeds, as serving to reproduce the species.

(4):

(n.) 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.