Streams in shaded woodland gullies, especially where there is some limestone, are also often rich in bryophytes.

Some of the mosses and liverworts that are found in Welsh rivers and streams are listed below.

Mosses

Amblystegium riparium

This is a common moss on wood, rocks and stones at or near the waters edge in slow-moving rivers and streams, canals, ditches and ponds. It forms loose matts flattened against the substrate, and with the leaves widely-spreading from the stem. The leaves are up to 4mm in length, tapering to fine points, and with a nerve running for about three-quarters their length.

Brachythecium rivulare

A common species in and by rocky streams. It has a glossy dark-green appearance, with the shoot tips often conspicuously lighter in colour. The leaves have a nerve runnig for about three-quarters their length, and distinct auricles.

Cinclidotus fontinaloides

This is a robust moss which bears a superficial resemblance to Fontinalis species (hence fontinaloides). Unlike those species, however, its leaves are distinctly bordered and have a nerve which runs the entire length. It grows in the flood zone of rivers.

Cryphaea lamyana

A rare species found on rocks and trees in the flood zone of rocky rivers. A fairly robust species with shoots having a cylindrical appearance, and often curved. The leaves are ovate with a nerve running about three-quarters their length. Cells are rounded. This is a Red Data Book species in Britain, and in Wales is only known from a section of the River Teifi. It is specially protected by inclusion on Schedule 8 of the Wildlife and Countryside Act.

Dicranella palustris

This is a very distinctive moss with its upright stems and spreading, translucent leaves. It is a characteristic moss of mountains streams where there is a slow trickle of water.

Fontinalis antipyretica

This is one of the few Welsh mosses which normally grows submerged in water. It is a robust species, dark-green in colour and with the leaves arranged on the stems in three ranks. The leaves are folded sharply in two equal halves, giving the appearance of a small boat. This is mainly a plant of slow-flowing rivers and streams. (The closely related Fontinalis squamosa has concave leaves, not sharply folded, and is found in fast-flowing waters).

Hyocomium armoricum

This densely-branched moss occurs abundantly in upland streams in Wales, forming carpets which are bright golden-green in colour, or darker with bright-green shoot tips. It is able to tolerate fast flowing water and can often be found by waterfalls.

Leskea polycarpa

This species occurs in very similar situations to the previous one, and is common. It is a slender plant, and has tiny leaves up to 1mm in length. The leaves are rounded in their lower half, then drawn to a pointed tip. Unusually amongst pleurocarpous mosses the leaf cells are rounded or hexagonal.

Myrinia pulvinata

This is another species associated with silt in the flood zone of rivers. It occurs only on tree boles an roots, however, and is much less common than the previous two species (it is listed as British Red Data Book species). . A slender plant, occurring in soft, dull-green patches with prostrate main stems and ascending branches.

Rhynchostegium riparioides

A robust species which grows on rocks low on the banks of streams or on rocks in the streams. The stems are often long and with few branches. Lower down they are often bare of leaves. The leaves are ovate, with fine teeth at their margin, and have a nerve running for three-quarters their length. The leaves tend to stand away from the stem. A common species.

Thamnobryum alopecurum

This is a common moss on shaded rocks in many streams and rivers in Wales (though not where the water is very acid). It is a robust, branched species, with a bright- to dark-green, almost blackish colour. Its stems are noticeably wiry. The manner of the branching (with the branches clustered toward the tips of the stems) gives the plant a tree-like (dendroid) appearance.

Tortula latifolia

This moss grows on silted tree bases and rocks and walls by the side of slow-flowing rivers and streams. It is usually confined to a zone subject to flooding, but not permanently submerged. It has leaves which are broadest above their middle, and with a nerve running the entire length (but not extending beyond the leaf tip as in most other species of Tortula). It is most common in the eastern half of Wales.

Liverworts

Anthelia julacea

This species forms dense tufts or wide cushions by mountains streams, dull bluish green when wet, and pale gray when dry. It is a slender plant, with leaves deeply divided and arranged in three ranks (the underleaves in this species are similar to the laterals). In the UK it is mainly confined to North Wales, North-West England and Scotland.

Chiloscyphus polyanthos

A leafy liverwort which forms loose prostrate mats of flattened shoots, with oblong, undivided leaves arranged neatly on either sideof the stem. Underleaves are present and divided into two sharp prongs. It grows on wet rocks or soil by streams and rivers.

Conocephalum conicum

This robust thallose liverwort grows on basic or neutral soil beside streams in wooded valleys, as well as other damp, shaded habitats. Its surface is marked with roughly hexagonal divisions, at the centre of each is a small pore, visible with the naked eye. When crushed the thallus gives off a distinctive scent.

Jubula hutchinsiae

A plant of very wet, shaded rocks in wooded ravines, especially around waterfalls and cascades, occurring as dark-green patches. It has leaves which are bilobed, with the very much smaller lobe helmet-shaped and the larger lobe coarsely toothed. Bi-lobed underleaves are present. In the UK it is calssified as Nationally Scarce; in Wales, it is most common in the North.

Porella pinnata

This is another plant which grows in the flood zone of rivers, on rocks, and less usually on tree-boles and roots. It is a fairly robust leafy liverwort, with leaves crowded and overlapping. The leaves are divided into two lobes, but with one lobe very much smaller than the other, lying underneath the larger, and adpressed to the stem. Oval-shaped underleaves are also present. This species is Nationally Rare in the UK, and is mainly confined to Wales and SW England, but may be locally abundant.

Riccia huebeneriana

A small thallose liverwort with a rosette-like habit. It is a colonist of recently exposed mud at the edge of ponds lakes and reservoirs, as well as rivers. It is a Red Data Book species in the UK and known from only a few sites in Wales. Where it does occur it can be in some quantity for relatively short periods of time (perhaps weeks), and then disappear again.

Scapania undulata

This is a very common leafy liverwort of upland streams (and also occurs in a wide variety of other wet habitats). In common with other Scapania species, its leaves are divided into two lobes, with the smaller folded back over the larger. The leaf margins are usually finely-toothed.