148 GUIDE TO THE STUDY OF LICHENS. 



tioned in the historical review. The HcBmatommas 

 have also found a place in the dyeing industries. 



3. Lecanora. 



The thallus varies from crustose to somewhat foliose. 

 It is highly probable that the Parmelias are the 

 direct descendants of the Lecanoras. The amateur is 

 likely to confuse the Lecanoras and Biatoras^ since 

 they resemble each other in their general characters, 

 especially the spore-characters. The foliose forms 

 have numerous small, more or less jjlicate, lobes which 

 are somewhat ascending and bear numerous rhizoids. 

 Color of the thallus varies from light-green to dark. 



The apothecia are generally plentiful; as compared 

 with the apothecia of the Biatoras they are quite large. 

 They are discoid, sessile, not immersed ; margin ex- 

 tending somewhat above the brown to nearly black 

 disk. Hypothecium colorless. 



The spores are simple, colorless, elliptical, some- 

 what variable in size and form. 



The Lecanoras occur upon bark and rock and have 

 a wide range. 



1. Lecanora lacustris. Thallus very thin, uniformly 

 spreading, indistinctly areolate ; reddish-brown. Apo- 

 thecia small, scattering, partially immersed, margin 

 somewhat raised. Disk reddish-brown to dark. Spores 

 rarely mature. 



2. Lecanora orosthea. Thallus thin, powdery to 

 finely granular, pale sulphur color. Apothecia of 

 medium size, margin barely raised, somewhat crenate. 

 Disk pale-brown. Spores ovoid, colorless, 14/* X 7.5/i. 



