148 



POPULAR HISTORY OF LICHENS. 



founded with Ramalina fraxinea, with which it frequently 

 grows, but from which it may readily be distinguished by 

 the flaccid, pendent thallus and the white colour of the 

 under side of the lacinige. In some localities it occurs 

 chiefly in a dwarfed, deformed, and very sorediiferous state ; 

 in such a condition we have found it abundant in the 

 woods around Floors Castle, Kelso."* It sometimes grows 

 also on stones and rocks, and even in a prostrate state on 

 the ground : of a trailing form of the variety stictocera we 

 have large specimens from Exmoath Downs, — the same lo- 

 cality where grows the peculiar articulated variety of Usnea 

 barbata. This species yields a gum, which was introduced 

 experimentally into Glasgow, as a substitute for gum-arabic 

 in calico-printing, by the late Lord Dundonald, but soon 

 fell into disuse. On account of this property also it has 

 been used as a demulcent in chest-complaints. From its 

 giving a peculiar and much-relished flavour to bread, it 

 was at one time much used in baking in Egypt ; for this 

 purpose, Forskuel says, it was imported in shiploads from 



* The ash of this sorediiferous variety was found by Mr. Wallace Lindsay 

 to contain the bases potash, soda, lime, magnesia, alumina, peroxide of iron, 

 and manganese, in combination with sulphuric, hydrochloric, and phosphoric 

 acids. 



