• Polyblastia cruenta (Körb.) P.James & Swinscow
Polyblastia cruenta
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This lichen of streamside pebbles and stony flushes is readily known by its grey-green (in shade) to brown (in well-lit sites) thallus and much-thickened spherical discs with smoothly convex tops occasionally with a nipple-like protruding tip (ostiole). Wetting often imparts an oily sheen to the thallus. The spores are muriform (many-faceted like a stained glass window), brown, and around 60-30ųm in size. There are eight per ascus. This is a distinctive lichen of damp, siliceous rocks, flushed pebbles and bedrock in mostly, upland areas. Widespread but thinly distributed in Ireland; probably much under-recorded.

Key characteristics

  • Brown thallus with perithecia on pebbles and rocks in flushes and by streams
  • Perithecia prominent, clasped tightly by the thallus. P. theleodes has larger, darker spores and a lumpy thallus; P. melaspora has smaller, darker, broadly oval spores and grows on more calcareous rocks.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Polyblastia cruenta (Körb.) P.James & Swinscow. [In] LichenIreland. Accessed on 2018-08-18.