234 



HERRE 



Common on rocks throughout North America and abundant with 

 us on stones in the foothills. 



THELOSCHISTACE^. 



Thallus fohaceous, leafy-lobed or f ruticose in some forms, attached 

 by rhizoids or by a holdfast, the structure dorsi- ventral or radial; 

 cortex on upper and lower sides or on all sides; alga Pleurococctis . 



Apothecia circular, sessile, terminal, marginal, or scattered, with 

 thalline margin ; epithecium granular or powdery, usually containing 

 chrysophanic acid; hypothecium clear; paraphyses simple, septate; 

 asci with 8 spores, these colorless, polar-bilocular or four-locular, the 

 cells joined by a narrow isthmus. 



KEY TO THE GENERA, 



A. Thallus foliaceous, dorsi-ventral, attached by rhizoids. 



LIX. Xanthoria 

 A A. Thallus f ruticose, with radial structure, more or less erect, 



attached by a holdfast LX, Theloschistes 



LIX. Xanthoria (Th. Fr.) Arn. 



Xanthoria Th. Fries, Gen. Heterol. Europ. 60. 1861. in part. 



Xanthoria Arnold, 



Xanthoria A. Zahlbr. Ascolichenes, 229. 1907. 



Thallus foliaceous, laterally expanded or ascendant, attached by 

 rhizoids, imbricately lobate, dorsi-ventral, with cortex on both sides. 



Apothecia circular, scattered over the surface, or marginal, sessile 

 or appressed, disk always yellow or orange, with thalline margin; 

 spores colorless, polar-bilocular. 



Species few, of very wide distribution. 



KEY TO THE SPECIES. 



A. Thallus minute or small, effuse, scattered 5. ramulosus 



A A. Thallus more or less orbicular, expanded, entire. 



B. Lobes expanded, entire, short, thick, crenate, often prui- 



nose I . parielina 



BB. Lobes many-cleft. 



C. Thallus small, effuse or stellate; more or less concealed 



by the small, very abundant apothecia 2. polycarpus 



CC. Thallus with granulose, powdery margins. 



D. On trees and dead wood; apothecia medium to large. 



3. lychneus laciniosa 

 DD. Onmaritime rocks; apothecia small.. 4. lychneus pygmaa 



