Wall moss – 3 for the price of 1.

A number of years ago we put a new pitched roof on the garage along with slate tiles. Along the edge of the roof just underneath the tiles was filled in with mortar. Over the past 2 to 3 years this has been colonised with moss, which is growing quiet thickly now. Now I find mosses very difficult to identify and rely on iSpot and the experts to guide me. We see moss growing on walls and roofs we see it every day, but it not until you really look that you find a completely different world to the one we are used to. 

It turns out that there are at least three different species in the photo below. Without Tim’s help, delivered via iSpot I would not have been anywhere near this number. These include from left to right Tortula muralis, Ceratadon purpureus, Bryum capillare.

T. muralis is a dioecious species, each plant is either male of female. This comes from Greek “dioecy”, meaning two households. It grows in neat cushions or patches no more than 1cm tall. At the tips of the leaves a long smooth “nerve” projects outwards. When the moss is dry this can give the moss a grey , hairy appearance.

T. muralis can be seen towards the right of the photo, with the upright sporophytes.


Distribution map form T. muralis from the NBN .

The distribution map above illustrates that T. muralis can be found across the UK. It also has a wide global distribution. It is the commonest moss found on bricks and stone (2). And we have some growing on the walls in the front garden. It also grows on concrete, roof tiles as well as on natural, base-rich rock. Less commonly it can be found growing on trees and wood (2).

Next on the ID list is Ceratodon purpureus. This too is a very common species, forming cushions which can vary in colour from yellow to green through to red/purple brown (2). As well as garage roofs it can be found growing on heathland and acidic grassland. It’s one of the pioneer species and is common on fire sites.

Ceratodon purpureus

The star of the show today though is Bryum capillare. I was lucky to capture the light shining through the water droplet on the swan neck sporophore.

Bryum capillaire swan neck sporophore.

It seems that my garden, or at least the roof is common. B. capillIare is also a common tuft forming moss. But unlike the other two the sporophyte has a swan neck shape. 

blurred close up of the leaves of Bryum capillare

The habitats where B. capillare can be found are widespread (2). These include, besides our roof, acidic spils, grassland, woodland rides, soil banks and waste ground. As well as roofs it can grow on fence posts, trees, logs, and rocks.

Before I started reading about mosses this afternoon I hadn’t appreciated that each clump is more a colony rather than a single plant. So that was an excuse to play with the digital microscope  I received for Christmas. The photo below shows this pretty well ( though I need to work on getting the lighting right). 

a single “plantlet” of Bryum capillare.

Mosses don’t have roots, but rhizoids, a name derived from the Latin prefix rhizo- for “root,”, but confusingly it is not a true root. The rhizoids anchor the moss to the surface from where it growing. Their function is to be the root system for the moss. But unlike roots, rhizoids do not have a xylem and phloem to carry water and nutrients to the rest of the plant. Like a tangled mass of silken white hair, the rhizoids can tie a plant to its substrate, whether it be soil, solid rock, or other material in which it grows. The multicellular nature of the rhizoid does allow movement of water and limited transport of minerals from the substrate.

The close up photo above reasonable illustration of the sporophyte of Bryum capillare

1: NBN Gateway.  Tortula muralis. https://data.nbn.org.uk/Taxa/NBNSYS0000036310/Grid_Map. Accessed 2015-03-08.

2: Atherton,I., Bosanquet, S. and Lawley, M. (2010) Mosses and Liverworts of Britain and Ireland: a field guide. British Bryological Society.


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