BRYOPHYTE LIFE CYCLE This cycle is the only cycle out of the four that is gametophyte dominant, which means it spends most of its time in the gametophyte stage. It also is one of the few that requires water for fertilization. This means that the sperm of one bryophyte must swim to an egg, and must live in areas where water is available as a constant supply.
The cycle starts when a spore lands on a moist area, germinates, and grows into a group of filaments called a protonema. As the protonema grows, it develops filaments into the ground and into the air, and eventually forms a bud and a moss plant. The sperm are held inside of the antheridia (or antheridium) while the egg is held inside of the archegonia (or archegonium). Many plants differ as some hold both sperm and egg on the same plant while others have them on separate plants. After the sperm reaches the egg through a raindrop, it fertilizes the egg and forms a diploid zygote. As the zygote grows, it reaches out of the gametophyte, and the mature sporophyte forms a sporangium on top of a long stalk. The sporangium holds the haploid spores, and once it ripens it opens up and releases the spores, starting the cycle over again.
EXAMPLES OF BRYOPHYTES Some examples of bryophytes are shown below, such as mosses (left), liverworts (middle), and hornworts (right).