Species Focus - Leucobryum sp.

There are about 850 taxa of mosses and liverworts in Wales, a substantial proportion of the bryophytes species that are found in the whole of Europe. Many of these species thrive in the comparatively warm, wet climate of North Wales but because they are so small they tend to be overlooked. One group that are recognisable are the Leucobryums or ‘White’ Mosses. They form dense cushions and hummocks in bogs, heathland and woodland. They can appear as large spreading masses, small compact cushions or sometimes form detached ‘moss balls’. They can also occur as epiphytes on trees.

Leucobryum cushions tend to be quite a pale green and turn a dirty white when they are dry, so they stand out from their surroundings. This is because of the unusual cellular structure of the leaves which have a middle layer of photosynthesising cells sandwiched between two layers of empty hyaline cells which make them look ‘whitewashed’! These hyaline cells act in a similar fashion to the hyaline cells of Sphagnum, facilitating the ability of the plant to take up water.

The leaves are 6-9mm long, erect and fairly straight, although they might be slightly turned to the side. They are appressed to the stem and overlapping when dry. The base of the leaf is quite broad tapering to a rolled tip.

Until a couple of years ago there were thought to be only two species of Leucobryum in the UK. However, it is now known that there are three species. L. glaucum grows in bogs and L. juniperoideumgrows in western ravines. The third species, L. albidum is found in slightly drier habitats but overlaps into the habitat of the other two so work is needed to determine its true distribution in North Wales.Certain identification can only be determined microscopically so it is not possible to record to species level in the field, but it would be valuable to have accurate information as to where these mosses are turning up. So, please submit records of Leucobryum using the ORS or the LERC Wales App, ideally with a photo and as accurate a grid reference as possible.