Source : Webster's Revised Unabridged Dictionary (1913)

Gemma \Gem"ma\, n.; pl. {Gemm[ae]}. [L., a bud.]
   1. (Bot.) A leaf bud, as distinguished from a flower bud.

   2. (Biol.) A bud spore; one of the small spores or buds in
      the reproduction of certain Protozoa, which separate one
      at a time from the parent cell.

Source : WordNet®

gemma
     n : small asexual reproductive structure in e.g. liverworts and
         mosses that detaches from the parent and develops into a
         new individual
     [also: {gemmae} (pl)]