ISO 



ous and are probably Cystococcus humicola, although that is not defi- 

 nitely determined, as they also show a close resemblance to Pleuro- 

 coccus vulgaris. 



The structure of the apothecia, indicates a near relationship to the 

 Graphidaceae. They are small, irregular in outline, though never 

 distinctly linear ; as in the other groups they begin their develop- 

 ment below the surface of the substratum which they break through 

 very early, but never project much above it. The hypothecium and 

 epithecium are black ; the shape of the paraphyses is very difficult 

 to determine ; they seem to form an anastomosing network of slen- 

 der granular hyphae. 



The spores are large, usually colorless or brownish, multilocu- 

 lar and constricted at the middle. 



The few representatives of this genus, seem to be southern in 

 their range, occurring upon trees. 



PLATE 32. 

 Mycoporum pycnocarpum Nyl. 



1. Natural size. 



2. Magnified portion. 



3 and 4. Section of apothecium and thallus. 



5. Paraphyses and spore-sac. 



6. Spores. 



7. Algae. 



7. Arthothelium Mass. Mem. Lich. 54. 1853. 



In the general structure of the thallus this genus shows a close 

 relationship with those Arthonias bearing Chroolepus umbrina ; in 

 fact many authors combine Arthothelium with Arthonia, and the 

 general description of the thallus of Arthonia applies to it as well. 



The apothecia are comparatively large, stellate in outline, agree- 

 ing in development and general structure with those of the preceding 

 groups. The epithecium is dark ; the entire thecium (exclusive of 

 spore-sacs) and hypothecium is of a dirty brown color, or it may be 

 colorless. The paraphyses are much branched or nearly simple, 

 though their structure is difficult to make out, because of their granu- 

 lar and gelatinous nature. The spore-sacs are large, colorless and 

 somewhat gelatinous at the upper end. 



The spores are large, colorless, multilocular and very distinct in 

 outline; there are eight in each spore-sac, which is not usual in 

 genera with such large spores. 



