SATURDAY 4th JANUARY 2014                                      PRAEGER CENTRE, NATIONAL BOTANIC GARDENS

LEADER: KATY DUFF

BOGS, MOSSES AND LIVERWORTS

 

Morning Session
Katy introduced us to members of the Sphagnum genus some of which are essential components of peat bogs.  34 species are known from Britain and Ireland but quite a significant number are limited in their occurrence having either a northern or western distribution. Others have become relatively scarce in Ireland as a result of the destruction of our raised bogs.

Sphagnum species, as non-vascular plants, have the ability to absorb water directly into their cells and have the resilience to quickly rehydrate after dry weather.

Using a simple key and hand lens (x20) we were shown how it was possible after some experience to separate Sphagnum species ‘in the field’ into Sections: Sphagnum, Subsecunda,  Acutifolia, (Rigida), Squarrosa and Cuspidata and then to identify the species using further characteristics. Important characteristics are the shape of branch and stem leaves. For example, members of the Section Sphagnum have a conspicuous stem cortex with thickness one third of stem radius. Ultimately some species will require microscopic examination for confirmation.  

The species on display included S. fallax, S. austinii, S. fuscum, S. tenella, S. magellanicum, S. papillosum, S. palustre and S. capillifolium.  

S. palustre Blunt-leaved Bog-moss (Sphagnum): Is rather variable in colour, forming large, untidy mats or loose hummocks which are green to yellow-brown. Characteristic are the swollen branches which are blunt-tipped because of the crowded concave branch leaves with their hooded tips. It may be found in moderately enriched sites, for example in wet woodland, ditches, stream margins and flushes.  

S. papillosum Papillose Bog-moss (Sphagnum): Forms mats and low hummocks and is generally pale ochre-brown. It never has a trace of red. The capitulum of centre and spreading branches are always similar in colour. Upper spreading branches are short and blunt-tipped….   Found in raised and blanket bogs it can be confused with S. magellanicum and S. palustre in certain circumstances.  

S. squarrosum Spiky Bog-moss (Squarrosa): Is usually bright green and spikey looking. Branch leaves are abruptly pointed and tapering with a tubular tip curved away from the branch.  

S. denticulatum Cow-horn Bog-moss (Subsecunda): Plants are green yellow-brown to dull coppery red. The outer capitulum branches are swollen and smooth in outline and the leaves have flat edges. Some of the branches are curved, with the leaves towards the tip appressed to each other tightly appressed to each other resembling a cow’s horn …..  

S. capillifolium Acute-leaved/Red Bog-moss (Acutifolia) : It is a hummock-former and is pale-green under heather and stem branches are usually ‘chaotic’ in structure. Erect stem leaves are triangular in shape. This species is often separated into subspecies capillifoium and rubellum.  

S. fallax Flat-topped Bog-moss (Cuspidata) : This species was at one time considered to consist of a larger number which are now amalgamated..It is a medium-sized green to mustard-brown growing in carpets. Capitula are convex and usually stellate with developing branches in neat pairs apparent between the capitula rays …. It is very common in wet habitats including nutrient poor fens and pools and runnels on bog and may be found with Soft Rush Juncus effusus.  

Afternoon Session
After lunch, participants presented a wide variety of bryophyte specimens for identification. These included a number of Sphagnum species, two of which were not on display during the morning session namely, S. subnitens a member of the Acutifolia Section that can resemble S. capillifolium, and S. cuspidatum, which grows in bog pools, whose appearance has been likened to a “drowned kitten”.

 When asked about the distinguishing features of S. palustre and S. papillosum, which are often confused, Katy explained that the former has long tapering branches, whereas S. papillosum has short stubby branches. Their habitats also differ: S. palustre prefers moderately enriched sites, such as the edge of bogs or flushes, while S. papillosum is typically found on raised or blanket bogs. However, she pointed out that sometimes microscopic examination might be necessary to make a definitive diagnosis.

A number of other bryophytes were also identified:

Odontoschisma sphagni, a thread-like liverwort with round leaves, was present in many of the Sphagnum samples examined. It is one of the commonest liverworts found on hummocks of Sphagnum.  

Leucobryum glaucum forms characteristic whitish mounds that are found under heather, or on burned bogs where they are more visible.   

Polytrichum commune occurs on bogs and heaths. It has tall, robust shoots, and toothed leaves. It is much larger than other Polytrichum species.  

Hylocomium splendens is a delicate fern-like, bipinnate moss. It resembles and grows in similar habitats to Thuidium tamariscinum. It differs from the latter by having a red rather than a green stem. 

Rhytidiadelphus triquetrus, is a very conspicuous bushy plant of calcareous woodland, in contrast to Rhytidiadelphus squarrosus, whose shoots have a starry appearance and which is ubiquitous in lawns and in unimproved grassland.  

Further Reading
Mosses and Liverworts of Britain and Ireland a field guide. British Bryological Society Edited by Ian Atherton, Sam Bosanquet & Mark Lawley (2010).
 

http://rbg-web2.rbge.org.uk/bbs/bbs.htm

British Mosses and Liverworts E.V. Watson. Cambridge University Press (1981).  Note: This publication has good microscopic illustrations but nomenclature is now out-of-date for some species.
Pat Lenihan & David Nash

   

S. papillosum                         S. squarrosum                        S. palustre

   

S. subnitens                S. squarrosum                       S. cuspidatum

     

S. magellanicum                          S. capillifolium sssp. rubellum                  S. fallax

     

Polytrichum commune     Rhytidiadelphus squarrosus     Rhytidiadelphus triquetrus

     

Hylocomium splendens     Leucobyrum glaucum

Photographs © P Lenihan 

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