Bryophytes are simple plants. They are the simplest plants that grow on land. There are three forms of bryophyte. These are mosses, liverworts and hornworts.
Bryophyta is the formal term for this division of plants who do not have tissues to move water. In some modern classifications the word bryophyta only includes mosses. However, the term is still useful because mosses, liverworts, and hornworts share important traits.
Scientists think that liverworts evolved from green algae. Then other plants, including moss and hornworts, evolved from liverworts.
A person who studies bryophytes is called a bryologist. The study of bryophytes is named bryology.
Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. A bryophyte has two forms that have different numbers of chromosomes. The haploid form has unpaired chromosomes. It is called a gametophyte. People often write "1n" for haploid. The other form is diploid and has paired chromosomes. It is called a sporophyte. People often write "2n" for diploid.
A bryophyte begins when its parent plant makes haploid spores that land on the ground. Each spore grows into a leafy gametophyte. This gametophyte is either male or female. Male gametophytes make haploid sperm. Female gametophytes make haploid eggs. Water moves the sperm to the egg. An embryo is made when they join. This embryo is diploid. It grows a tall stalk from the gametophyte. This stalk is often brown. A structure called the sporangium is at the top of the stalk. The sporangium is diploid too. It makes spores that are haploid in a process called meiosis. When the spores land on the ground, the cycle begins again.
Bryophytes are "gametophyte dominant." This phrase means when you look at a bryophyte, you are more likely to see the gametophyte. The sporophyte is less common. Sporophytes are always attached to the gametophyte. They must get food from the gametophyte. Bryophyte sporophytes do not have branches. They make only one sporangium.
- The British Bryological Society