Order: Arthoniales       Family: Opegraphaceae Species: Opegrapha niveoatra Growth type crustose. Identification confirmed by John Douglass Photos: On Laburnum. Kinsale, Co. Cork, SW Ireland. Thin dull-grey to olive-brown thallus, similar to O. vulgata but with shorter lirellae, to 1mm long. Scattered or contiguous apothecia, discs becoming partly exposed, exciple +/- uneven, but thalli are often sterile. Spores are 4-7(-8) septate, 20-30 x 2.5-4 µm. Pycnidia are abundant, the conidia short, curved and worm-like. Micrograph below. Chemical reactions negative. Found on neutral and basic-barked trees; Ash, Sycamore and Elm. Most frequently recorded from eastern Ireland. Similar: Opegrapha vulgata. Larger discs, conidia sickle-shaped

Micrograph

Opegrapha niveoatra May 2010