The prothallus is the gametophyte, i.e. it bears gametes-male (antherozoid) and female (ovum), and reproduces by the sexual method. Spores remain alive only for a few days. Under favourable conditions their germination begins and gives rise to prothalli. The prothallus is the gametophyte since it bears antheridia or archegonia or normally both.
Sporophyte bears spores and reproduces by the asexual method. On the under surface of the leaf or the sporophyll a number of dark brown structures, pale green when young, may be seen; these are called sori. Each sorus is a group of sporangia.