121 



Section I. GTMNOCAEPL 



Nat. Ord. I. U8NEACE2E* 



Family Character. — TJiallus filamentous : filaments round, 

 having a cartilaginous or leathery cortical layer, which is very 

 liable to crack and separate in annular fragments from a central 

 thread of white, cottony, medullary tissue, — giving the thalline 

 filaments a peculiar articulated and sometimes a moniliform ap- 

 pearance. Apoihecium peltate, terminal on the thalline filaments, 

 which appear as if dilated at their extremities into a flattened, 

 somewhat irregularly rounded disc ; margin radiate-ciliate, pale 

 flesh-coloured, or colour similar to that of thallus. 



Genus I. USNEA, DHL 



Name said to be derived from the Arab Aclineh or AcJinen 

 [Axneeh or TJsnee according to Dillen)/a generic term for 

 all Lichens. 



* The student will derive much assistance from examining named and dried 

 specimens of British or foreign species as contained in the following works : — 

 Leighton, Lichenes Britannici exsiccati, 1851, published in fasciculi, of which 

 several have appeared : Bohler's Lichenes Britannici : Schserer, Lichenes 

 Helvetici exsiccati, 24 fasciculi, last dated 1852 : Mougeot and Nestler, 

 Stirpes Cryptogamicse Vogeso-Rhenanse, 10 fasciculi, 1813, last dated 1833 : 

 Tuckerman, Lichenes Americse Septentrionalis exsiccati, 2 fasciculi, 1847: 

 Fries, Lichenes Suecici exsiccati : Massolongo, Lichenes Italici exsicc. 



