The Verrucarias as above limited seem to be quite cosmopolitan ; 

 their usual habitat is rock. The majority of so-called tree Verru- 

 carias belong to other genera. 



PLATE 56. 



Verrucaria rupestris Schrad. 



1. Natural size. 



2. Apothecium and portion of thallus magnified. 



3. Section of apothecium. 



4. Section of thallus. 



5. Galatinous paraphyses and spore-sac. 



6. Spores, a, simple forms ; b, septate forms. 



7. Hyphae and algae (Pleurococcus vulgaris.) 



7. Pertusaria DC. Fl. Franc. 2: 319. 1895. 



This group is usually placed near Urceolaria among the Parme- 

 line lichens. There is, however, no reason why it should be 

 given such a position ; the apothecial characters indicate the true 

 relationship which is doubtless with the Verrucariaceae, close to 

 Tryfethelium. and Pyrenula. It is affirmed that some Pertusarias 

 have apothecia resembling those of Lecanora, thus indicating a re- 

 lationship to the Parmeliaceae ; such a resemblance seems to exist 

 in the higher European forms of this genus. In all the species 

 which came to my notice from our territory the apothecia are globose 

 and immersed either in the substratum or in the thallus. The close 

 relationship to Trypethelium is very apparent from a critical study 

 of P. -pustulata which is one of the lowest representatives of the 

 genus ; in this species the thallus and apothecia are almost entirely 

 hypophloeodal, the latter occurring in clusters forming warty ele- 

 vations of the bark ; the apothecia open by very minute, almost 

 imperceptible pores. In the majority of Pertusarias, however, the 

 thallus inclusive of apothecia is epilithic or epiphloeodal. To these 

 the following general description applies. 



The thallus is essentially crustaceous in its general appearance ; 

 there is, however, a fairly well developed upper cortical layer ; the 

 medullary tissue is also well developed ; no lower cortical layer is 

 present, the entire thallus being closely adnate to the substratum by 

 means of the numerous rhizoidal hyphae ; the upper surface is 

 almost smooth, warty to papillose ; the thallus is quite variable in 

 thickness and in the higher European forms the thallus becomes 



