762 LICHENES. 
Distribution and Numbers.—Lichens are distributed over all 
parts of the world. The pulverulent species ‘ are the first plants 
that clothe the bare rocks of newly formed islands in the midst 
of the ocean, foliaceous lichens follow these, and then Mosses 
and Liverworts.’ lLichens also form a considerable proportion 
of the vegetation of the polar regions and of mountain-tops. 
Illustrative Genera :—Opegrapha, Pers. ; WVerrucaria, Pers. ; 
Lecidea, Ach.; Cladonia, Hofim.; Peltigera, Hoffm.; Usnea, 
Hoffm. There are above 2,500 species. 
Properties and Uses.—Several possess nutritive properties 
from containing aimylaceous substances, and such are also 
emollient and demulcent: others contain bitter principles, which 
render them tonic and astringent ; and many are important as 
dyeing agents. A few possess aromatic properties. Some Lichens, 
as species of Variolaria, contain a large amount of calcium 
oxalate. None are known to be poisonous. 
Cetraria.—C. islandica, Iceland Moss.—'This lichen contains about 70 
per cent. of lichenin or lichen starch, and above 2 per cent. of a crystalline 
bitter principle termed cetraric acid or cetrarin. It is ofticial in the British 
Pharmacopceeia, and is employed as a nutritious food, and as a mild muci- 
laginous tonic in catarrh, consumption, and other affections. When used 
for food it should be previously deprived of its bitterness: this may be done 
either by heating it once or twice in water to near the boiling point of 
Fahrenheit, or, still better, by digesting it in a weak alkaline solution formed 
by adding half an ounce of carbonate of potassium to about a gallon of cold 
water, and afterwards washing it with water. 
Cladonia or Cenomyce.—C. rangiferina is the Reindeer Moss. It is so 
termed from constituting the food, more especially in the winter months, of 
the Reindeer.— Cladonia ( Scyphophorus) pyxidata is commonly termed Cup- 
moss ; this and other species have been employed as remedies in whooping- 
cough. 
Gyrophora (Umbilicaria).—Several species, denominated tripe de roche, 
possess nutritive qualities, and are used as food in the Arctic regions. 
Franklin and his companions owed their preservation in 1821, in a great 
measure, to the use of these lichens as food. The Gyrophoras also possess 
slight tonic properties owing to the presence of a bitter principle-—G. pus- 
tulata is one of the Lichens used in this country by the manufacturers of 
orchil and cudbear. (See Roccella and Lecanora.) It may be also made to 
produce a brown colour. 
Lecanora.—L,. tartarea was formerly the principal lichen used in the 
preparation of the dye called Cudbear ; but cudbear is now obtained not 
only from it, but also from a number of other Lichens, as the species of 
Roccella, &c. (See Roccella and Gyrophora).—L. Perella yields a similar 
dye. Two species of Lecanora, namely, L. esculenta and L. affinis, form 
important articles of food both to man and animals generally, in Persia, 
Armenia, Tartary, &c. They appear in some seasons in such enormous 
quantities, that in ‘certain districts they cover the ground to the depth of 
several inches, and the natives believe they fall from heaven. L. esculenta 
is also found in Algeria, Asia Minor, &c., and Dr. O’Rorke has endeavoured 
to prove that this ‘lichen was the manna of the Hebrews,—that which fed 
them with regularity for forty years in the wilderness. 
Parmelia.—P. parietina was formerly regarded as a valuable febrifuge, 
astringent, and tonic. It contains a yellow crystalline colouring matter, 
called chrysophanic acid, which is identical with that obtained from Rhubarb, 
Goa powder, &c.—P., perlata is employed by the manufacturers of orchil 
