\Spore\, n. [Gr. ? a sowing, seed, from ? 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.
Note: 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},
      {O["o]spore}, {Restingspore}, {Sph[ae]rospore},
      {Swarmspore}, {Tetraspore}, {Zo["o]spore}, and
      {Zygospore}.
   (b) An embryo sac or embryonal vesicle in the ovules of
       flowering plants.
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.
{Spore formation}.
   (a) (Biol) A mode of reproduction resembling multitude
       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.