LICHENES. 133 



II. Thallus subfoliaceous, consisting of scales attached to the sub- 

 stance on which they grow and more or less combined together. 

 Apothecia always bordered and discoid, sessile (patellulce). 



Fam. VIII. SquamarieIe. 



15. Psora. Thallus defined, thick, formed of distinct flattish 

 or convex tubercles or scales. Apothecia (patellulce) bordered, 

 plane, at length convex, placed at the side of the scales, the 

 border of the same colour as the disk. 



16. Squamaria. Thallus denned, scaly, spreading, orbicular 

 and stellate, the scales distinct or adherent, often imbricated, 

 diverging. Apothecia {patellulce) bordered, the border of the 

 same substance and colour as the thallus. 



17. Placodium. Thallus denned, orbicular and stellated, the 

 scales adherent, indistinct, subpulverulent, foliaceous in the cir- 

 cumference. Apothecia {patellulaz) in the centre of the thallus, 

 bordered, the border of the same colour as the disk. 



III. Thallus loose, scarcely attached, except by fibres or radicles 



or a small base, to the substances whereon it grows. 



A. Upper surface different from the vndcr. 



a. Attachment of the thallus diffuse, {not fixed by a central point ). 



a. Apothecia scutelliform, discoid, bordered, attached by the centre 



(scutellai). 



* Thallus more or less membranaceous. 

 Fam. IX. Parmeliacejk. 



18. Parmelia. Thallus foliaceous. membranaceous or cori- 

 aceous spreading, lobed and stellated or laciniated, more or less 

 fibrous beneath. Apothecia (jscutella) orbicular, beneath form- 

 ed of the thalluRj i'wi\ fixed only by a central point, disk bon- 

 pave, colouredi its border formed by the indexed thallus. 



19. StIcta. Thallus foliaceous, coriaceo-cartilaginous, 

 spreading, lobed. free and downy beneath, with little cavities or 

 hollow spots (cyphelke) often containing :i powdery substance. 

 Apothecia (scutella i beneath formed of the thallus to which they 

 are suppressed and fixed by a central point, the disk coloured, 



plan*', surrounded by an elevated border formed of the thallus. 



*#• 



Thallus ( in a moist state) of G gelatinous tUOStatUX . 



r \ m. \. Coli im \i i 



20. Collema, Thallus entirely of 6ne substance, gelatinous, 

 when dry generally becoming hard and cartilaginous, poly- 

 morphous, granulated, foliaceous, lobed, laciniated of branched. 

 Apothecia (scutellc > orbicular, sessile (randy substipitate,) bar* 



