Large numbers of liverworts and hornworts grow in New Zealand, mostly in damp forests. They form spongy green mats on the forest floor, rocks and trees. People often think they are mosses, because the three types of plant look similar.
Life cycle of liverworts and hornworts
The green parent plant releases sex cells (eggs and sperm). When an egg and a sperm join together within the plant, a spore capsule sprouts on a stalk. This stays attached to the parent plant and depends on it for nutrients. Spores escape from the capsule, germinate, and grow into a new generation of plants that produce sex cells.
New Zealand has more than 500 species of liverwort.
They can be grouped into two main types:
- Leafy liverworts. They vary widely. Some have hairy leaves that trap water and delay drying out. Others have water sacs, which contain bacteria and tiny, swimming animals.
- Thalloid liverworts. These have no leaves. Complex thalloid liverworts are thick sheets of cells, with internal air spaces and pores (tiny holes) to the outside. Simple thalloid liverworts are thin sheets of cells, with no pores.
Their name comes from the horn-like shape of their spore capsules, where they make and store their spores. There are 13 species in New Zealand.
Hornworts grow as a flat green mass on soil or rocks.