Microglossum olivaceum
Description
Microglossum olivaceum a species of fungus belonging to the family Geoglossaceae. Earth tongues are one of the groups of fungi that are indicators of old unfertilized grassland. Unlike most other members of this group, this species is usually easy to identify due to its unusual colors. 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. Found in old semi-natural grasslands in habitats ranging from upland acidic grassland to dunes to neutral grasslands and man-made habitats like churchyards.
Common names: Olive Earthtongue, Earth Tongue Fungus.
Mushroom Identification
Ecology
Traditionally reported as saprobic; growing alone to gregariously in moss under hardwoods; summer and fall; widely distributed in North America; infrequently collected.
Fruiting Body
15–30 mm high and 2–5 mm wide; club-shaped to somewhat flattened and irregular; head and stem not clearly separated to the naked eye, but under a loupe or dissecting microscope separated by a slight color difference.
Head
Cylindric to club-shaped; sometimes becoming somewhat flattened, grooved, or irregular; bald; dull yellow to yellowish-brown.
Stem
Cylindric; bald; colored like the head but very slightly darker.
Flesh
Brownish to yellowish; unchanging when sliced.
Odor and Taste
Not distinctive.
Chemical Reactions
Iron salts olive, then dark gray on the surface of the head.
Microscopic Features
Spores 12–15 x 3.5–5 µm; subfusiform, with one side a little more flattened than the opposite, more convex side; smooth; with one to several large oil droplets; hyaline in KOH. Asci subclavate; smooth; hyaline to yellowish in KOH; 85–100 µm long. Paraphyses 100–120 x 1.5–2.5 µm; usually projecting; filiform-cylindric; subflexuous; apices subclavate, subcapitate, subacute, or merely rounded; smooth; yellowish to hyaline.
Similar Species
The only other species that this could be confused with is Microglossum viride which has a brighter green color. M. viride has a stem that is often covered in green scales compared to the smooth stem of M. olivaceum, has longer spores and is usually found in woods and not grasslands. This latter distinguishing feature cannot be relied on, however, as grassland species are also found in woods in Northern Ireland so the other features should always be checked.
History
In 1796 when Christiaan Hendrik Persoon described the Olive Earthtongue he gave it the binomial scientific name Geoglossum olivaceum. It was the French mycologist Claude-Casimir Gillet (1806 - 1896) who in 1879 transferred this species to the genus Microglossum - a new genus circumscribed by Gillet in that same year - whereupon it acquired the scientific name Microglossum olivaceum by which it is generally known today.
Microglossum, the genus name, means small tongue, while the specific epithet olivaceum refers to the olive tinge to most of the fruitbodies (but note that the color is very variable with some being much browner than others).
Synonyms of Microglossum olivaceum include Geoglossum olivaceum Pers., Leptoglossum olivaceum (Pers.) W. Phillips, Mitrula olivacea (Pers.) Sacc., and Microglossum fuscorubens Boud.
Photo sources:
Photo 1 - Author: epopov (CC BY 4.0)
Photo 2 - Author: frank103 (CC BY 4.0)
