Irish lichens

Arthonia astroidestera

Order: Arthoniales       Family: Arthoniaceae

Species: Synarthonia astroidestera (Arthonia astroidestera)

Growth type crustose.
Photos: On Holly. Glengarriff woods, Co. Cork, SW Ireland.
Identified by John Douglass

Immersed whitish or creamy yellow thallus, usually bordered by a thin brown line. Very small brown apothecia, irregularly branched or +/- stellate, usually thickly pruinose. Spores are oblong-ovoid, usually 4-septate with an enlarged upper cell. Pycnidia absent.
Thallus: K-, C-, P-. Pruinose apothecia: UV+ bright orange-yellow.

Rare, occurs on smooth-barked trees (especially Holly) in humid areas of old woodlands.

Similar: Arthonia stellaris. Spores 3-4 septate with enlarged upper cell but apothecia are non-pruinose and UV-

Arthonia astroidestera

Arthonia astroidestera

Arthonia astroidestera, UV+ reaction
Arthonia astroidestera November 2010

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