“ It also yields a peculiar modification of chlorophyll, called thallochlor, fumaric acid, licheno-stearic acid and cetraric acid, to which last it owes its bitter taste. It forms a nutritious and easily digested amylaceous food, being used in place of starch in some preparations of cocoa. It is not, however, in great request, and even in Iceland it is only habitually resorted to in seasons of scarcity. ”

“ It grows abundantly in the mountainous regions of northern countries, and it is specially characteristic of the lava slopes and plains of the west and north of Iceland. It is found on the mountains of north Wales, north England, Scotland and south-west Ireland. ”