i8o 



The spores are normally colorless and eight-celled ; in form 

 they are spindle-shaped ; the plasmic portions are somewhat dia- 

 mond-shaped, two obtuse angles closely approaching each other near 

 a transverse septum. 



Much confusion exists in the limitation of this genus, some au- 

 thors uniting Trypethelium and Pyrenula in one, but it seems more 

 consistent to keep them separate, since the spore-characters are very 

 marked in both genera ; only a very few species occur in the terri- 

 tory ; many of the forms described as Trypethelium belong to Pyren- 

 ula. 



This genus is essentially southern ; the species occur upon trees, 

 forming patches of considerable extent; they are evidently, closely 

 related to some of the Sphaeriaceae ; the immediate fungal ancestors 

 require further study. 



PLATE 51. 



Trypethelium virens Tuck. 



1 . Plants natural size, a, apothecial colony. 



2. Semidiagramatic section through apothecia and substratum (mag- 



nified) a, apothecium developing below the suhstra turn ; b, mature 

 apothecium. 



3. Section of apothecium. 



4. Algae and hyphae of the very rudimentary thallus. 



5. Paraphyses and spore-sac. 



6. Spores. 



2. Pyrenula Ach. Lich. Univ. 64. 1810. 



This genus closely resembles Trypethelium. The thallus and 

 apothecia are hypophloeodal, the latter opening by a pore at ma- 

 turity. In by far the greater number of species the thallus is quite as 

 rudimentary as in the preceding genus, but in the higher forms the 

 algal colonies ( Chroolepus) are quite apparent. The fungal ances- 

 tors are evidently derived from the Sphaeriaceae. In fact, there is 

 little doubt that many herbarium specimens catalogued as species of 

 Pyrenula are really fungi ; careful study of the specimen is neces- 

 sary to demonstrate the absence or presence of a thallus. 



In the majority of the representatives of the genus the apothecia 

 are quite uniformly scattered ; in some they form colonies, as in 

 Trypethelium. The superimposed corky layers of the substratum un- 



