About Calicium trabinellum (Ach.) Ach.
Calicium trabinellum, commonly known as the yellow-collar stubble lichen, is a widespread pin lichen species belonging to the family Caliciaceae. It was first formally described in 1803 by Swedish lichenologist Erik Acharius, who originally published it as Calicium xylonellum ß trabinellum. Acharius published the accepted new combination Calicium trabinellum in a later chapter of the same 1803 publication. The lichen's thallus typically appears as a visible stain on the wood it grows on. Its apothecium has the form of a small black pin: it has a stalk 0.5–0.9 mm (0.02–0.04 in) tall that supports a black mound of ascospores, which is called a mazaedium. The underside of the mazaedium is covered in a powdery pruina, which contains vulpinic acid. This compound gives the pruina its characteristic yellow colour. The spores of Calicium trabinellum have roughly textured walls, and their dimensions are 7–10 by 4–6 μm. This lichen is common on dead wood in boreal and hemiboreal forests. It has been recorded from Africa, Asia, Europe, and North America.
