416 



ECONOMIC AND TECHNICAL 



various dye-species, and Hoffmann, as already stated, gives illustrations of 

 colours that can be obtained. It has been once and again affirmed that 

 Parmelia saxatilis yields a red colour, but Zopf 1 denies this. It contains 

 saxatillic acid which is colourless when extracted but on boiling gives 

 a clear reddish-yellow to reddish-brown solution which dyes wool and silk 

 directly without the aid of a mordant. Zopf 1 observed the process of dyeing 



Fig- 135. Parmelia omphalodes Ach. (S. H., Photo.}. 



followed in South Tyrol : a layer of the lichen was placed in a cooking pot, 

 above this a layer of the material to be dyed, then lichen and again the 

 material until the pot was filled. It was covered with water and boiled 

 three to four hours, resulting in a beautiful rust-brown and peculiarly fast dye. 



Reddish- or rust-brown dye is also obtained from Haematomma ventosurn 

 and H. coccineum, a yellow-brown from Parmelia conspersa (salazinic acid), 

 and other shades of brown from Parmelia perlata, P. physodes, Lobaria pul- 

 monaria and Cetraria islandica. 



Yellow lichens in general furnish yellow dyes, as for instance Xanthoria 

 parietina which gives either brown or yellow according to treatment and 

 Cetraria juniperina which forms a beautiful yellow colouring substance on 



1 Zopf 1907. 



