In all bryophytes fertilization is dependent on water—usually a film of water or the splashing of raindrops—for the transfer of sperm to the egg. Chemical stimuli direct the motile flagellate sperm to the archegonium. The fertilized egg (zygote) grows out of the gametophyte, which is also the source of its nourishment. Typically the sporophyte is a slender stalk from 1 to 2 in. (2.5–5 cm) long, with a capsule at the tip; in some species it may be green and manufacture some of its own food. Cells within the capsule undergo meiosis (reduction division) to produce haploid spores. In many mosses the capsule has a lid, the operculum, which is shed, releasing spores. In other bryophytes the mature capsule ruptures in other ways to release spores.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.