26-Feb Mosses and Liverworts

There are bog, feather, thread, cushion and fork hair mosses, which can be hard for the amateur to differentiate. Mosses in London with distinctly curved tips are usually Dicranum or Dicranella spp. Mosses found partially submerged in water in boggy situations are often Sphagnum mosses. Cushion mosses mentioned last month e.g. Bryum spp., Grimmia spp., and Tortula spp. all tend to form small cushions on walls whereas turf mosses tend to form a carpet-like covering on the ground e.g. Barbula spp., Ceratodon purpureus and Funaria hygrometrica, the last species preferring to grow on old bonfire sites.

The swan’s neck thread moss Mnium hornum is one of the most common and most attractive of all London mosses. It forms robust clumps of vivid green leaves on the woodland floor especially around the roots of trees. Its English name refers to the elegant shape of its spore-bearing capsules. A similar species, which is also common, is the wavy-leaved thread moss Atrichum undulatum. As its name suggests, this can be recognised from the wavy outline around the edge of its leaves.

On shady clay banks, often not far from water, another handsome moss stands out i.e. the yew-leaved fork moss Fissidens taxifolus. This can be recognised by its finely cut leaves as its name suggests. Among any luxuriant mosses that form feather-like soft carpets you may well also find the tamarisk-leaved feather moss Hypnum tamariscinum.

In drier conifer woodland, or in beech woods, another very noticeable moss is the white fork moss Leucobryum glaucum. This forms large grey-green cushions that can hold water like a sponge. This characteristic is unfortunately leading to its decline, as Londoners collect it for their floral arrangements.

The mosses mentioned here are just a small selection from a large London list. They are either very common or just stand out when encountered for one reason or another. Their English names as so often can give a slight clue which can help a field identification.

Liverworts, except for one or two, tend to stand out far less than mosses and therefore often go unnoticed. There are two types: thalloid and leafy. The thalloid type look like small, green miniature mats of seaweed. These are usually found covering the banks of streams in woodland. The leafy liverworts can be more easily confused with mosses but tend to have paler, thinner leaves. Thalloid species such as the wide-nerved liverwort Pellia epiphylla are more likely to be noticed. These may well now be producing their fruiting bodies.

They are unusual-looking long, clear, glass-like threads with black, shiny capsules on top which may have already burst, revealing the spores within. Yet another equally common and unusual thallose liverwort is the crescent-cup liverwort Lunularia cruciata, so named because of the tiny crescent moon shaped cups on its flat green surface. These contain the reproductive gemmae which look like little green eggs in tiny nests. These eggs get splashed out by rain and then go on to form new plants. This they do so successfully they are really weeds of the liverwort world, often seen covering the soil surface of many a garden pot plant.