384 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



hydrophobia are quite imaginary. Cenomyce i^yxidata and its 

 allies have been recommended for hooping-cough. Sticta pul- 

 monacea is so bitter in Sweden, that it is sometimes used as 

 a substitute for hops. Alectovia Arahum has the reputa- 

 tion of being sedative, and Evernia vuVpina is said to be 

 poisonous to wolves. Evernia prunastri was formerly used 

 as a material for hair-powder, from its white colour, amyla- 

 ceous nature, and supposed power of retaining odours. It has 

 been observed by Dr. John, that Lichens which grow on the 

 top of fir-trees contain more than an ordinary portion of oxyds 

 of iron.* Parmelia parietina is still sold by the herbalists. 

 It has been recommended in Germany as a substitute for 

 Cinchona bark, and was used in other cases where astringents 

 are necessary, as it had been previously by Haller and Wille- 

 met. It affords also a beautiful test for alkali, the yellow 

 decoction assuming a beautiful red tint. Cenomyce rangi- 

 ferina is a most important vegetable wherever rein-deer are 

 kept, supplying a large portion of their food, and one which 

 from its nature is as luxuriant in winter as in summer. The 

 deer have only to scratch up the snow where it abounds, and 

 they have at once an abundant and nutritive food, which has 

 the advantage, when dried up by the long biu-ning days of an 

 arctic smnmer, of being restored at once to its suppleness on 

 the first returning shower. 



425. There is one economical purpose to which Lichens are 

 applied — viz., dyeing ; in which they are of some importance. 

 While some, as Parriielia loarietina and Evernia vulpina, 

 yield colouring matter under the form of chrysophanic and 

 vulpinic acids, others contain colouring princij)les, which, 

 though without colour in themselves, afford beautiful tints when 

 treated with alkalies. Yellows and browns are afforded by the 

 two Lichens above-mentioned, and Umbilicaria pustulata, 



* It is supposed by Sclmedermaun, that the red spots which are some- 

 times found at the base of Ceiraria islandica, are due to the presence of 

 cetrarate of iron. The brown discoloration is probably due to cetra- 

 rate of ammonia, arising from the cetraric acid imbibing ammonia from 

 the air. Similar explanations may possibly be given of the discolora- 

 tion so common in other lichens. 



