Bryophytes is the common name given to a diverse group of non-vascular plants that reproduce through alternating cycles of sexual and asexual or vegetative reproduction. This process uses both a sperm and an egg for the sexual reproduction, and spores alone for the asexual cycle.
The term bryophytes is used to refer to species of three separate phyla known as Bryophyta, Anthoceratophyta and Hepatophyta, which are mosses, hornworts and liverworts respectively. There is much debate as to whether these three should be classified together or separately, although all three groups share some similar characteristics, such as being non-vascular.
These plants lack veins to transport water throughout their system. This mostly restricts them to living in moist places, as their lack of roots means they can only take in water that comes into direct contact with them. Non-vascular plants are also quite limited in size for this same reason.
Scientists have classified approximately 10,000 known species of mosses, 7,000 species of liverworts and 200 hornworts. It is thought that bryophytes evolved from green algae, but that the two groups evolved separately and independently. Scientists also believe bryophytes were most likely the earliest type of plants that evolved to live on land.