The family of fungi known collectively as 'earthtongues' are aptly named. The shape of the upper part of the fungus, called the head, closely resembles a grooved and flattened animal tongue. There are a number of species within this family of fungi, but only one other in the genus Microglossum. That fungus, M. viride, is a woodland species, has a scaly stem or 'stipe', and is a dark olive-green. M. olivaceum has a smooth stipe, and appears to be far more variable in colour. Some are pale brown, others similar but darkening towards the top of the head. There are also records of this species that have dark brown heads and turquoise stipes.
WARNING: many species of fungus are poisonous or contain chemicals that can cause sickness. Never pick and eat any species of fungus that you cannot positively recognise or are unsure about. Some species are deadly poisonous and can cause death within a few hours if swallowed.
Very little is known about this fungus apart from the fact that it is thought to be an indicator of ancient, un-improved grassland, and often occurs in association with a range of waxcap fungi. In the Brecon Beacons it occurs on short turf that has developed over ancient lime-kiln waste, and on the former track beds of railways, all known to be over 25 years old and probably nearer 100 years. It may have an association with dead vegetation, particularly mosses. This behaviour is known as 'saprophytic', from the Greek words sapros 'rotten' and phuton 'plant'. Any organism that lives off the dead remains of plants is called a saprophyte.
Fungi are thought by some to be better indicators of change in land use than many plants. Although we know of a great many different species, very little is known about the relationships most of these fungi have with other plants or, indeed, other organisms. There are many species of plants that only grow well if their roots are associated with a particular species of fungus. The fungal threads living under the ground attach themselves to the roots of the young plant and greatly improve the plant's chances of obtaining water and nutrients for growth. In the case of orchids, many of them cannot germinate at all without the right fungal partner.
The sites for this species are widely scattered. The most recent records are from the New Forest and mid Wales, where it is known from over 25 sites in Brecknock, Radnor, Carmarthen and Ceredigion, with outliers on the Gower peninsular and near Caerphilly. There are single sites in Lancashire and Devon, and it also occurs in Northern Ireland. This fungus is found across northern Europe and appears to be declining across most of its range.
The most obvious threat to this species is the reduction in grazing or cutting of grassland, as the fungus needs short turf. Another is 'improvement' of its grassland habitat, by use of animal manure or artificial fertilisers. This process reduces diversity by encouraging the more dominant grasses to take over. There is also the threat posed by land-use changes such as tree planting and the spread of scrub, as well as the ploughing and reseeding of grassland.
Microglossum olivaceum is listed in the UK Biodiversity Action Plans and included in English Nature's Species Recovery Programme. Along with the British Mycological Society and the Countryside Council for Wales, the plant conservation charity Plantlife has been running a survey of grassland fungus called the Waxcap Grassland Survey. Waxcaps, like M. olivaceum, are good indicators of ancient grassland habitat. In fact, one new record for the earthtongue was obtained near Bristol during a waxcap survey.
The future of this intriguing fungus will depend on the preservation and careful management of the grasslands where it and its associated fungi are found. More work is also planned to improve our knowledge of the intricate relationships that exist between plants, animals and fungi. For too long we have regarded fungi with dread, fear and loathing. Now, we are starting to find out just how important a role they play in the life and the health of our planet
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