Petractis clausa Incertae sedis
Petractis clausa

Growth type crustose
Chemical reactions negative. Photobiont Scytonema (cyanobacteria)

On +/- damp, partly shaded, highly calcareous rocks, loose limestone and chalk pebbles

Endolithic whitish or yellowish-white thallus with immersed urceolate apothecia that leave pits in the rock when they decay. Discs pinkish to pale orange, spores mostly 3-septate with distinct perispore, (15-)17-23(-35) x 5-7 Ám excluding perispore. Microscope photographs below.

Similar: Petractis nodispora, photobiont Trentepohlia.
Gyalecta jenensis, photobiont Trentepohlia, submuriform spores


Petractis clausa

Petractis clausa

Microscope photographs
Petractis clausa

Petractis clausa

Petractis clausa
Petractis clausa
Canford Magna and Ulwell Gap, Dorset. January 2016

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