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Arthonia radiata Arthoniaceae
Arthonia radiata

Growth type crustose
Chemical results negative. Epithecium brown or olive-brown, K+ pale green

Pioneer species, very common on smooth-barked trees and shrubs. Sometimes host to Muellerella polyspora, Stigmidium arthoniae, spores 17-23 x 4-5 µm, 1(-3) septate and Opegrapha arthoniicola, the spores 3-septate (10.5-)12.5-14.5 x 3.4-4.2(-4.8) µm.

The small patches of white, pale-grey or olive-brownish thallus are often surrounded by a black prothallus. Crowded, black, rounded or star-shaped apothecia are not pruinose. Asci are 8-spored, the spores 3-septate, upper cell not enlarged, 15-20 x 5-7 µm. Micrographs below.

Similar: Coniocarpon cuspidans (Arthonia elegans). Thallus often tinged yellowish, apothecia K+ red-purple,


Arthonia radiata

Arthonia radiata

Microscographs
Arthonia radiata

Arthonia radiata
Arthonia radiata
Dorset. 2012, 2016, 2019

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