Irish lichens

Opegrapha calcarea
Order: Arthoniales       Family: Roccellaceae

Species: Opegrapha calcarea

Growth type crustose, graphid.
Opegrapha calcarea includes O.conferta, O.chevallieri, O.saxatalis and other former species.

Variable. Thin or immersed thallus with black, unbranched lirellae to 1.2mm. Lirellae can be star-shaped, slit-like or form piled heaps. Asci are 8-spored, spores 3-septate, 16-20 x 4-5(-6.5) Ám. Microscope photograph below.

Occurs on shaded calcareous or basic rocks and on man-made substrates. Also found on shaded basic to acidic coastal rocks.
Thallus: chemical reactions negative.

Similar: Opegrapha cesareensis. Lirellae to 2mm, spores 4-5 septate, 15-22 x 4-5 Ám.

Opegrapha calcarea       Opegrapha calcarea

Opegrapha calcarea

Microscope photograph
Opegrapha calcarea
Opegrapha calcarea on coastal rock, Creagh, County Cork. February 2009

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