THALLOGEX^. 713 



important as dyeing agents. (See Dr. Lauder Lindsay's 

 papers on Lichens, in Transactions of the Royal Society of 

 Edinburgh.) A few possess aromatic properties. Some lichens, 

 as species of Variolaria, contain a large amount of oxalate of 

 lime. None are known to be poisonous. 



Gi/rophora.—Severa.\ species, denominated tripe dc roche, possess nutritive 

 projjerties, and are used as food in the arctic regions. Franlilin and iiis com- 

 panions owed their preservation in 1821, in a great measure, to the use of these 

 liciiens as food. The Gyrophoras also possess slight tonic properties, owing 

 to the presence of a bitter principle. G. pustulata is one of the lichens used 

 in this country by the manufacturers of orchil and cudbear. (See Roccella.) It 

 may be also made to produce a brown colour. 



Lladonia or Cenomyre C. rangiferina is the Reindeer Moss. It is so 



termed, from constituting the food, especially in the winter months, of the 

 Keindeer. Cladonia pyxidata, or Scyphophorus pyiiduta, is commonly termed 

 Cup-moss; this and other species, have been employed as remedies in hooping- 

 cough. 



Parmelia parietina, was formerly regarded as a valuable febrifuge, astrin- 

 gent, and tonic. It contains a yellow, crystalline, colouring matter, called 

 chrysophanic acid, which is identical with the yellow colouring principle of 

 rhubarb. P. perlata is employed by the manufacturers of orchil and cudbear. 

 (See Roccella.) 



Variolaria. V. dealbata and V. oreina, are used for the production of orchil 

 in France. 



Lecmora L. tartarea, was formerly the principal lichen used in the pre- 

 paration of the dye called Cudbear. Cudbear is, however, now obtained, not 

 only from it, but "also from a number of other Lichens, as the species of Roc- 

 cella, &c. (See Roccella.) L. Perella yields a similar dye. Two species of 

 Lecanora, namely, L. esculenta and affinis. form important articles of food 

 both to man and other animals 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 that 

 they fall from heaven. L. esculenta is also found in Algeria, .Asia Minor, &c., 

 and Dr. O'Rorke, in a recent communication, has endeavoured to )irove that 

 this substance was the true manna of the Hebrews, — that which fed them with 

 regularity for forty years in the wilderness. 



Sticta pulmonaiia. Tree Lung-wort, Oak-lungs. — This lichen possesses 

 tonic and nutritious properties, resembling in these respects, the Cetraria 

 islandicus. In Siberia, it is used instead of hops for imparting bitterness 

 to beer. It is also employed in France, &c. for the production of a brown 

 dye. 



Peltigera or Peltidea canina, and P. rufescens are known in the herb shops 

 of this country under the name of Ground Liverwort. This was formerly offi- 

 cinal in the London Pharmacopoeia, and regarded as a specific in hydrophobia. 



Cetraria islandica. Iceland moss.— This lichen contains two kinds of 

 starchy matters — one called lichen starch, and the other inulin; it also contains 

 a bitter principle {cetrarin). It is officinal in our pharmacopoeia and is 

 employed as a nutritious food, and as a mild mucilaginous tonic in catarrh, 

 consumption, &c. When used for food only, it should be previously deprived 

 of its bitterness ; this may be done, either by heating it twice in water to near 

 the boiling point of Fahrenheit, or by digesting it in a weak alkaline solution 

 formed by adding half an ounce of carbonate of potash to about a gallon of 

 cold water, and afterwards washing it with water. C. nivalis possesses some- 

 what similar properties. 



Roccella. Ori liella Weeds.— R.fuciformis. tinctoria, hyjpomccha,fiaccida f 

 and their varieties, under the common name of Orchella Weed, are the 

 species commonly met with in this country. They are imported from various 

 parts of the world, as the Canary and Cape de "Verd Islands, the Azores, 

 Angola, Madagascar, Mauritius, Madeira, South America, Cape of Good 

 Hope, &c. In commerce they receive the name of the country from whence 

 they have been derived. Orchella weed is extensively used in this country and 

 elsewhere in the manufacture of purple and red colouis, called or cA/Z or archil, 

 and cudbear. In Holland a blue colour, called litmus, is also prepared from 

 the same lichens. Other lichens, as species of Lecanora, Gyrophora, Par- 



