• Arthonia muscigena Th.Fr.
Arthonia muscigena
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This tiny, crustose epiphyte grows well on elder twigs, on elm and sycamore in sheltered situations. Find it on elder first so you might know it again. The thin, grey-brown thallus forms miniscule patches (less than 5mm wide) with irregularly rounded discs (to 0.3mm diam.) which resemble specks of black jelly. A microscope squash shows peg-shaped, one-septate spores (8-12 x 2.5-4.0Ám). Thinly scattered in Ireland, scarce in the south-west.

Key characteristics

  • A microlichen, most commonly seen on elder twigs
  • In the field it can look like a speck of twig dirt; spores one-septate, peg-shaped.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Arthonia muscigena Th.Fr.. [In] LichenIreland. Accessed on 2020-09-18.