190 GUIDE TO THE STUDY OF LICHENS. 



study; at present it is generally included under Lepto- 

 gium. 



1, Polychidium muscicolum. Tliallus small, fruti- 

 cose, much branched, lobes cylindrical, dark to olive- 

 black. Apothecia medium, discoid upon the older 

 basal branches. Disk flattened to concave, brown. 

 Spores typical of the genus, 25;a X 8/x. 



This lichen is found growing over moss, on rocks, 

 and occurs at great altitudes. It frequently occurs on 

 high rocks facing the ocean. 



6. Heppia. 



Thallus of medium size, foliose,- monophyllous, 

 closely adnate to the substratum ; margin more or less 

 lobed ; brown color, becoming quite dark with age. 

 Rhizoids numerous. The algse are perhaps a species 

 of Scytonema. 



The apothecia are comparatively large, innate in 

 concave depressions of the thallus, a characteristic not 

 occurring in any other lichen-genus. The hypothecium 

 is colorless. Disk reddish-brown. Spores are colorless, 

 simple, thin-walled with granular contents, and vari- 

 able in size and form. 



1. Heppia Despreuxii. Thallus foliose, monophyl- 

 lous, margin lobate, closely adherent to substratum, 

 dark. Apothecia typical of the genus. Spores typical, 

 22/t X 9/^. 



There is perhaps only one authentic species in exist- 

 ence. The European specimens labelled H. urceolata 

 and H. adglutinata are in all respects similar. H. 

 Despreuxii is southern and occurs upon sandy soil. 



