Fungalpedia – Note 2651, Merismatium
Merismatium Zopf.
Citation when using this data: Meng QF et al. – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank, Fig 1.
Classification: Verrucariales genera incertae sedis, Chaetothyriomycetidae, Eurotiomycetes, Pezizomycotina, Ascomycota, Fungi
The lichenicolous genus Merismatium was established by Zopf (1898) to accommodate the type species M. lopadii, transferred from Celidium lopadii Anzi. This species has muriform, brown spores and grows on Lopadium pezizoideum (Ach.) var. muscicolum in the alpine region of the Tyrolean Alps. It is characterized by small, black, apothecia that only emerge at the apex from the thallus of Lopadium, with a pierced apex. The perithecia are dark brown, and the hymenium is wine-colored when treated with iodine. The spores are spindle-shaped, brown and oval.
In Species Fungorum (2025), Merismatium lopadii is listed as synonymy of M. nigritellum which was transferred from Verrucaria nigritella Nyl. by Vouaux (1913). However, there is no record of M. lopadii being treated as a synonym of M. nigritellum in the original reference, so M. lopadii is still kept in the list of Merismatium.
Merismatium was placed in the Dothideales incertae sedis by Eriksson et al. (1987), later, Triebel (1989) proposed to place it within Verrucariales, and recognized species as two groups: those with spores having a distinct perispore (halo) and those lacking this feature, but retained both groups within Merismatium. Hafellner (2011) revised this genus and restricted it to species with thin-walled, non-halonate ascospores. Species with thick-walled ascospores provided with a halo were classified into another genus as Halospora.
To date, 13 species are recognized in Merismatium according to Index Fungorum (2025) and MycoBank (2025), all of which are lichenicolous. No sequence data is available in NCBI.
Type species: Merismatium lopadii (Anzi) Zopf.
= Celidium lopadii Anzi.
Other accepted species: Species Fungorum – search Merismatium
Figure 1 – Merismatium lopadii redrawn from Zopf (1898). a Asci and paraphyses. b Ascospores.
References
Eriksson O, Hawksworth DL. 1987 – Notes on ascomycete systematics. Nos. 225–463. Systema Ascomycetum 6, 111–165.
Entry by
Meng QF, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand and School of Public Health, Zunyi Medical University, Guizhou 563000, China.
Published online 1 July 2026