Mosses

Mosses, liverworts and hornworts are collectvely called Bryophytes.  They are small flowerless green plants that reproduce through spores or asexually via gemmae or tubers.  Unlike flowering plants, ferns and conifers, they have no vascular system (the phloem or xylem vessels of flowering plants, ferns, conifers etc.)  Instead, water and nutrients diffuse directly into their thin tissue.  As early colonisers they can be found in virtually all terrestrial habitats. As well as being all around us, they are a good option to study in January and February when most other plants and invertebrates are absent.

Liverworts are in a separate NatureSpot gallery - they are either 'thallose' or 'foliose' (leafy), the latter with flattened shoots and leaves arranged in 2 or three ranks. Be aware that some mosses e.g. Fissidens and Plagiothecium have flattened shoots and can look similar to leafy liverworts.  Hornworts are rarely recorded in Leicestershire and Rutland, and currently NatureSpot does not have any records with images that can be displayed.

Facebook Group: Bryophytes of Britain and Ireland

The British Bryological Society provides some excellent online guidance to help identify mosses and liverworts.

The BBS guides to common mosses and liverworts are very useful.

Atherton, I., Bosanquet, S. & Lawley, M. (eds.) 2010. Mosses and Liverworts of Britain and Ireland: A Field Guide  BBS  is an accessible guide for non-specialists and is highly recommended. The BBS are currently planning a second edition.

Watson, E.V. (1981) British Mosses and Liverworts (3rd edition)  CUP has keys that are more technical, often based on cell shape and leaf characteristics that may require microscopic examination. Be aware that since it was published, there have been some changes in taxonomy, and some new species have arrived in the British Isles.  

Smith, A.J.E (2004) The Moss Flora of Britain and Ireland (2nd edition) CUP is the classic guide to mosses, illustrating all species known to occur in the British Isles and including a comprehensive key - essential for the serious bryologist.

To identify some mosses, you may need to look at the microscopic details of the leaves - e.g. the cell shape in different parts of the leaf; whether there is a nerve in the leaf; whether the leaf margin is toothed, etc.  For most species, the leaves are just one cell thick, and the shape of cells can be seen at low magnification.  The BBS website includes micro-photographs of the leaves of some species, and the drawings in Watson and Smith (refs. above) are very helpful.  To begin with you will need to decided if the moss is a Sphagnum, or is acrocarpous or pleurocarpous.

Pleurocarpous mosses have a mat-like growth, with many branched stems tangled together.

Acrocarpous mosses have tufted growth made up of separate upright shoots, often forming dense cushions.

Moss specimens will keep for a long time in paper packets (not plastic) once they have dried out. They re-hydrate very quickly once water is added.

If you know of other websites or books that you would recommend, do let us know: info@naturespot.org

Bog-mosses (Sphagnum)

Sphagnum species of moss live in bogs or very wet ground, often associated with moor and heathland.  Their structure means they can hold water like a sponge.  They decay very slowly and some species are peat-forming, gradually building up a layer of peat to form mires, raised bogs and blanket bogs.  These are some of the most important habitats in the British Isles.  Their ability to hold water means that the blanketing Sphagnum bogs on our uplands help to regulate water flows and mitigate the impact of heavy rainfall.  Conservation and restoration of these habitats, such as on the Peak District in Derbyshire, is a priority in the battle to reduce flash flooding downstream in rivers like the Derwent.

Sphagnum is very common in upland areas of the north and west of the British Isles, but is scarce in lowland regons like Leicestershire and Rutland.  In our area, a few colonies of a few species survive in wet acidic condiions, such as on the higher parts of Charnwood Forest and in the former coalfield area of the north-west Leicestershire, often in mining subsidence flashes.   As well as nutrient-poor acid bogs and wet heaths, they can also be found in more base-rich habitats such as marsh, fen, wet woodland and the edges of ponds.  But in VC55, they are under threat; the habitat is vulnerable to loss or degradation through changes to drainage, to nutrient enrichment, natural succession and lack of management, and to climate change. 

Individual species are difficult to identify, most requiring careful field notes backed up by microscopic examination. The upright stems are clothed in spirally arranged branches ('fascicles'), forming a compact rosette-like head ('capitulum') at the stem tips.  The fascicles usually have spreading and pendant branches.  Branch and stem leaves are usually very different in shape.  Under the microscope, the leaves are seen to be a mesh of narrow green cells and larger transparent ('hyaline') cells.  The capsule is raised on a short stalk and is ovoid or globular; it is similar across the species and is not used for identification. 

In shade, they are usually green but develop secondary pigmentation in sunlight, often colouring with red, pink or orange tints; this can help in identifying a species. For some species, colour changes can also happen later in the year.  They dry out to a pale green, but rapidly re-hydrate and regain coloration. 

Many keys separate the species into one of 6 Sections: Sphagnum, Acutifolia, Rigida, Cuspidata, Subsecunda or Squarrosa, which is a useful starting point.  Based on this, ID features include:

• The colouration of well-grown plants growing in unshaded places
• The presence of and width of a stem cortex of hyaline cells (easily seen under low power magnification of a thin stem section);
• The appearance, number and arrangement of spreading and pendant branches;
• The shape of branch leaves – e.g. narrow, wide, hooded, acute, pinched at stem apex (best seen under low power magnification or hand lens);
• Whether the stem leaves are erect, hanging or spreading;
• The shape of the stem leaves - triangular, tongue-shaped (lingulate), fringed (fimbriate), etc. (best seen under low power magnification);
• The microscopic detail of the leaves – e.g. presence of fibrils, pores or papillae under high magnification (use of a stain will help to see these);
• Whether the green cells are more exposed in the adaxial (concave) or abaxial (convex) leaf surface, or equally (seen either in thin leaf section of by focussing up and down two leaves, one facing ‘up’ and the other ‘down’, under high magnification).

A helpful guide is Godfrey, G. & Rogers, K. (2021) Sphagnum mosses: field key to the mosses of Britain and Ireland.  FSC (Aidgap series)  

Sphagnaceae