About Cetraria islandica (L.) Ach.
Cetraria islandica (L.) Ach. is a lichen that typically has a pale chestnut color, though its appearance varies considerably – some specimens are almost entirely grayish-white. It grows 7.6 to 10.2 centimetres (3 to 4 inches) tall, with channeled branches that form flattened lobes with fringed edges. It grows abundantly in mountainous regions of northern countries, and is a particularly characteristic species of the lava slopes and plains of western and northern Iceland. In the British Isles, it can be found on the mountains of north Wales, northern England, Scotland, and south-west Ireland. In North America, its range covers Arctic regions from Alaska to Newfoundland; it extends south through the Rocky Mountains to Colorado, and also occurs in the Appalachian Mountains of New England. This lichen is a known host for the lichenicolous fungus Lichenopeltella cetrariicola, a species documented in Europe and Iceland. All parts of Cetraria islandica are edible. It is often dry in winter, but can be soaked for use, and boiling reduces its natural bitterness. It may be added as a thickener to milk or grains, or dried and stored for later use. It is not in high demand today; even in Iceland, it is only occasionally used in folk medicines and a small number of traditional dishes. In earlier times, it was much more widely used in foods such as breads, porridges, and soups. It forms a nutritious, easily digested amylaceous food, and has been used as a replacement for starch in some preparations of hot chocolate. Cetraric acid, also called cetrarin, is a compound found in this lichen. It appears as a white micro-crystalline powder with a bitter taste, and is readily soluble in alcohol, while only slightly soluble in water and ether. Alternative medicine sources have recommended it for medicinal use in doses of 2 to 4 grains (0.1 to 0.25 grams), as a bitter tonic and aperient. It is also traditionally used to relieve chest ailments, irritation of the oral and pharyngeal mucous membranes, and to suppress dry cough.
