Mosses and liverworts are plants which belong to a group called the Bryophytes, which are the oldest land plants on earth and have been around for some 400 million years. Bryophytes’ are tiny plants which are mainly green in colour and are flowerless, and which reproduce by spores and/or by asexual gemmae or tubers. There are three main taxonomic groups which are: Bryophyta (Mosses), Marchantiophyta (Liverworts) and Anthocerotophyta (Hornworts).
All these plants have evolved separately, and worldwide there are around 10,000 species of moss, 7,000 species of liverwort, and 200 species of hornwort. In Britain there are 763 species of moss, 300 species of liverwort, and just 4 species of hornwort. Most bryophytes have erect or creeping stems and tiny leaves, but hornworts and some liverworts have only a flat thallus and no leaves. Bryophytes have a two-stage life cycle. The gametophyte generation is the green photosynthetic part, where we see the green leafy plant we are mainly familiar with. Then there is the sporophyte generation which consists of a stalk and capsule which are dependent on the gametophyte for support and nutrients. The capsule when ripe releases thousands of tiny spores. Sexual reproduction occurs on the gametophyte generation and requires water for fertilisation. Many bryophytes also produce ‘gemmae’: tiny buds, discs or leaf fragments which spread the plants vegetatively.
Most Bryophytes can be seen all year round, and are therefore quite noticeable during the winter months. Many thrive in damp conditions, which is why Britain and Ireland have around two-thirds of European species, and some of our rarer species are globally rare. These extraordinary plants are like miniature forests, and are very important in sustaining the natural balance of ecosystems, and as primary pioneer species they help other plants and animals gain a foothold in the colonisation of new ground.