Microglossum olivaceum - Olive Earthtongue

Taxonomy

Phylum: Ascomycota

Class: Leotiomycetes

Order: Leotiales

These tiny greenish or brownish earthtongues are not only rare by very small and well camouflaged against the background of mosses and plant leaves in the kinds of unimproved grasslands in which they occur.

This picture was taken in Pembrokeshire by David Harries, with whose kind permission it is shown here are in Pat O'Reilly's new book Fascinated by Fungi, published by First Nature in September 2011.

The Olive Earthtongue is a BAP species. It is very similar to Microglossum viride, the Green Earthtongue, which has a scaly stem, whereas the stem of the Olive Earthtongue is smooth. The two can be separated with certainty by microscopic examination: the asci of Microglossum olivaceum are shorter than 100µm whereas the asci of Microglossum viride are longer than 110µm and can be up to 150µm. (As a further check, the spores of the Green Earthtongue are much larger than those of the Olive Earthtongue.)

Identification guide

Description	Like other earthtongues, this very rare species comprises a narrow stem supporting a wider, usually flattened head that does indeed look like a wrinkled tongue protruding from the earth. The colours of the Olive Earthtongue are very variable and should not be used as the sole means of identification. The fertile tongue section may be reddish or brown, medium olive-brown or dark greenish-olive, and vary from 0.8 to 2cm long and up to 1cm wide. The infertile stem is 2 to 6mm in diameter and 1 to 3cm long, smooth and varying in colour from bottle green through various shades of olive or occasionally brown.
Spore print	White.
Spores	Ellipsoid, 13 to 17 x 3.5 to 5µm.
Odour/taste	No significant taste or odour.
Habitat	In unimproved grassland.
Season	Summer and autumn.
Occurrence	Very rare and localised.
Similar species	Microglossum viride, a woodland species, is usually much greener and has a scaly stem; it also differs in microscopic characteristics.