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Anisomeridium viridescens

Ascomycota › Dothideomycetes › Monoblastiales › Monoblastiaceae › Anisomeridium

Description

A very thin whitish or pale-fawn stain on bark, sometimes pinkish when fresh. Scattered black perithecia are minute, about 0.1–0.2 mm across.

Source: ITALIC — Anisomeridium viridescens

Chemistry

Thallus: K−, C−, KC−, P−, UV−. The brown involucrellum turns green with K in a microscopic section; this is distinct from a thallus spot test.

Source: ITALIC — Anisomeridium viridescens

Habitat and Substrate

A pioneer on smooth young hazel bark in woodland, including abandoned coppices; occasionally recorded on holly.

Source: ITALIC — Anisomeridium viridescens

Similar Species

Eopyrenula species and small Naetrocymbe species can look similar. Confirm identification using microscopic characters.

Sources: ITALIC; BLS identification revision

How to Identify

Use the Anisomeridium key; assess the K+ green involucrellum, branched pseudoparaphyses, spores and conidia.

Source: BLS identification revision

Important Links

ITALIC — description, chemistry and images

British Lichen Society — species account and British distribution

GBIF — taxonomy and global occurrence records

Fungi of Great Britain and Ireland — species images

ITALIC — Anisomeridium identification key

AFL — alphabetical photographic index (general resource)

Identification Bibliography

Cannon, P., et al. (2023). Perithecial genera I. Revisions of British and Irish Lichens, 37, 1–59.

Nimis, P. L., et al. ITALIC: The Information System on Italian Lichens. Online account: Anisomeridium viridescens.

For identification, use the relevant key and compare the microscopic characters and chemical reactions. Photographs alone may be insufficient for closely similar crustose species.

Anisomeridium viridescens (Coppins) R.C. HarrisThallus crustose, ecorticate, poorly evident, usually appearing as a whitish to pale brown stain on bark, sometimes with a pinkish hue when fresh. Perithecia black, 0.1-0.2 mm across, circular to ellipsoid, mostly scattered. Involucrellum brown, K+ green; exciple brown in upper part; paler and thinner in lower part, of cellular hyphae, usually without bark cells; pseudoparaphyses 0.8-1 µm thick, persistent, much branched and anastomosing, the cells 4-10 µm long; periphyses absent. Asci 8-spored, obclavate to short-cylindrical, K/I-, fissitunicate, the apical dome with an indistinct ocular chamber, 31-49 x 11-17 µm. Ascospores, 1-septate, hyaline or sometimes turning pale brown when overmature, usually constricted at septum, the upper cell wider than the other, both cells usually biguttulate, without a median constriction, 12-17(-19) x 3.5-4.7 µm. Pycnidia black, 0.04-0.05 mm across, producing either: a) oblong, 2-3-guttulate macroconidia measuring 9-11 x 2-2.5 µm, or, b) ovoid-oblong to bacilliform, eguttulate microconidia measuring c. 4-5 x 1-1.3 µm. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.

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