98 



We must content ourselves with a consideration of the groups of 

 fungi (families) from which the various phyletic series of lichens 

 were most likely derived. 



i. The Pezizaceae. — There is considerable morphological evi- 

 dence that the fungal portion of the Caliciaceae is derived from some 

 ancestral form or forms of the Pezizaceae. Although the generic 

 groups of the Caliciaceae are closely related it is not likely that they 

 are derived from a single fungal ancestor ; Acolium, for example, 

 which, as a lichen is but little higher than Calicium, is very probably 

 derived from a different fungal group, as seems apparent from the 

 absence of the stipe. In the lichens of our territory there is a wide 

 gap between Acolium and Sfhaerofhorus ; the representatives of the 

 latter genus are certainly highly developed as lichens and it is wholly 

 impossible to determine the exact relation of their fungal ancestor to 

 the fungal ancestor of Acolium. Its apothecial and spore-characters 

 indicate, however, that it is derived from the Pezizaceae. 



It must also be remembered that the evolution of lichens has no 

 essential relation to the evolution of the ancestral fungal forms. 

 The Caliciaceae doubtless form the lowest group of lichens, but their 

 fungal ancestors are derived from almost the highest group of the 

 Ascomycetes. 



2. The Patellariaceae . — The fungal ancestor of the majority of 

 lichens is derived from the Patellariaceae. This large group of 

 Ascomycetes differs from the foregoing in the absence of a stipe. 

 The apothecia are discoid and sessile upon the mycelial network. 

 Not only are the various lichen-families derived from different groups 

 of the Patellariaceae, but likewise the various generic groups of 

 lichens. In the family Physciaceae it seems probable that the dif- 

 ferent genera form a natural series derived from a common fungal 

 ancestor ; this, however, is a mere conjecture and is impossible of 

 proof. In still other instances several lichen-genera are doubtless 

 represented by a common fungal ancestor as Collema, Lcftogium, 

 Mallotium and Hydrothyria. 



3. The Phacidiaceae. — The fungal ancestors of the Graphidaceae 

 are no doubt derived from this family of the Ascomycetes. The 

 apothecia are small, irregular in outline or linear, or rarely discoid 

 (Rocella). The fungal symbiont of Grafihis is very likely derived 

 from the genus Hysterium as is indicated by the spore as well as the 

 apothecial characters. 



