THE 



LICH EN-FLOR A 



OF 



GREAT BRITAIN, &e. 



CLASS OF LICHENS. 



ThaUus furnished with a stratum of gonidia or granula gonima 

 variously disposed, very often (at least in the orustaceous species) 

 containing crystals of oxalate of lime. Fructification consisting 

 of spores in thecse or asci ; gelatina hymenea in most species 

 becoming blue, in others reddish, on the application of an aqueous 

 solution of iodine. Spermogonia in pyrenodine conceptacles distinct 

 from the apothecia, and occurring either generally on the same 

 thallus with the apothecia (monoecious), or sometimes separately on 

 different thalli (dioecious). 



Lichens are distinguished from Fungi by the peculiar type, form 

 and structure of the thallus. The families and their principal sub- 

 divisions are chiefly based on the diversities of the thallus, though 

 sometimes the differences of the apothecia and spermogonia de- 

 termine these. 



Thallus byssaceous. = Family I. BYSSACEI. 

 ThaUus gelatinous. = Family II. COLLEMACBI. 

 Thalamium cellulose, with superimposed theciferous cavities = 

 Family III. MYRIANGIACEI. 

 ThaUus not gelatinous. = Family IV. LICHENACEI. 



Fam. I. BYSSACEI. 



Thallus byssaceous ; granula gonima in a thalline vagina. = 

 Tribe I. Sirosiphei. 



Fam. II. COLLEMACEI. 



Thallus filiform, branched. = Tribe I. Lichinbi. 

 Thallus membranaceous, lobate. = Tribe II. Collemei. 



Fam. III. MYRIANGIACEI. 



Thalamium cellulose, with superimposed theciferous cavities. = 

 Tribe I. Myriangiei. 



