Litmus was originally derived from several species of Roccella found in Africa. Litmus is a purple substance that turns red in acid and blue in alkali. This lichen is edible cooked. Soaking in a couple changes of cold water will help to remove the bitterness. During drought years the plant may be broken apart by the wind and blown across the land.
Reindeer moss is bitter, antibiotic, and edible.
The lichen is used as an expectorant to stimulate the release of phlegm, apparently due to the bitterness. This bitterness needs to be removed to make the plant edible. Montana Indians washed and soaked the lichen, then cooked it for one to two days in a steam pit. The cooked lichen was eaten or dried and powdered and used as a mush or thickener later. This bright yellow tree lichen contains a highly toxic acid.