n. [ Gr. &unr_; a sowing, seed, from &unr_; to sow. Cf. Sperm. ] 1. (Bot.) (a) One of the minute grains in flowerless plants, which are analogous to seeds, as serving to reproduce the species. [ 1913 Webster ]

☞ Spores are produced differently in the different classes of cryptogamous plants, and as regards their nature are often so unlike that they have only their minuteness in common. The peculiar spores of diatoms (called auxospores) increase in size, and at length acquire a siliceous coating, thus becoming new diatoms of full size. Compare Macrospore, Microspore, Oospore, Resting spore, Sphaerospore, Swarmspore, Tetraspore, Zoospore, and Zygospore. [ 1913 Webster ]

(b) An embryo sac or embryonal vesicle in the ovules of flowering plants. [ 1913 Webster ]

2. (Biol.) (a) 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. (b) One of the parts formed by fission in certain Protozoa. See Spore formation, belw. [ 1913 Webster ]

Spore formation. (a) (Biol) A mode of reproduction resembling multiple fission, common among Protozoa, in which the organism breaks up into a number of pieces, or spores, each of which eventually develops into an organism like the parent form. Balfour. (b) The formation of reproductive cells or spores, as in the growth of bacilli. [ 1913 Webster ]