gemma

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An asexual budlike propagule capable of developing into a new individual, as in liverworts.

from The Century Dictionary.

• noun In botany and zoology, a bud; that which is budded; the result of gemmation.
• noun [capitalized] In conchology, a genus of bivalve mollusks, of the family Veneridæ, containing a single small species, G. totteni or G.gemma (originally Venus gemma), about one eighth of an inch long, yellowish or rosy-white tipped with amethystine, found on the Atlantic coast of the United States. The young are retained inside the valves of the parent till their shells are formed.
• noun In biology, one of the hypothetical units of living matter: similar to biogen, idioblast, pangen, plasome, etc.
• noun A knoblike protuberance or nodule.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A leaf bud, as distinguished from a flower bud.
• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun bud; an asexual reproductive structure, as found in liverworts and hydra, able to produce new individuals from a cluster of cells.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun small asexual reproductive structure in e.g. liverworts and mosses that detaches from the parent and develops into a new individual