Chrysothrix candelaris

Chrysothrix candelaris, commonly known as the mustard powder lichen or gold dust lichen, is a species of leprose (powdery) lichen in the family Chrysothricaceae. It typically grows on tree bark, although it has also been recorded growing on rock. It does not show ascocarps or other reproductive structures, belonging to the group commonly known as the 'Fungi or lichens imperfecti' in the UK.

Distribution
This lichen is widespread and common in the United Kingdom, where it occurs on the bark of deciduous trees, especially rugged old specimens, such as sycamore, alder, oak, willow, beech, and pine species, normally in dry shaded parts. and occasionally on the sheltered faces of siliceous rocks. It is found in North America, Scotland, Hungary, Iran, Latvia and has been recorded in the Cape Verde Islands.

Description
As suggested by its name, C. candelaris is bright yellow, orange-yellow, or greenish-yellow. It has a powdery (leprose) appearance, a superficial thallus and lacks apothecia and isidia. Because its thallus is made entirely of powdery soredia that covers the substrate like a crust, Chrysothrix candelaris is a leprose lichen.

Laundon described three chemotypes of this species: one with the chemical cyclin, one with, and a third with both of these compounds.

Life cycle
Lacking apothecia, soredia and isidia, C. candelaris is not able to reproduce by spores, but spreads by its thallus becoming distributed by the wind, the feet of animals, etc. to suitable habitats.

Miscellaneous
This lichen can be used as an indicator to monitor air quality.