178 



even stated that some of the groups are devoid of paraphyses, which 

 is, however, not the case, as closer examination will clearly show. 

 Frequently the cell-walls of the paraphyses are so much gelatinized 

 that their outline is not distinguishable ; in such cases it is usually 

 possible to trace the direction of the cells by the granular plasmic 

 contents. 



The great differences in the spore characters indicate a polyphy- 

 letic origin. The fungal ancestors are doubtless to be found in the 

 Pyrenomycetous groups Sphaeriaceae and Massariaceae. 



Two forms of algae predominate in this family. Chroolepus 

 umbrina occurs in the genera from Tryfietkelium to Verrucaria. 

 Exceptionally Cystococcus humicola occurs in certain species, whether 

 constantly or not I am at present unable to state. Pleurococcus vul- 

 garis Menegh. occurs in Verrucaria, Dermatocarfon and Endocar- 

 j>on, where it seems to have become greatly modified in size and form 

 (see Thecial Algae) ; it may, however, be possible that the alga is 

 not Pleurococcus vulgaris, though the culture experiments of Stahl 

 and others seem to prove that such is the case. 



It is also evident that many intermediate forms of this family are 

 wanting, as, for instance, the connecting links between Verrucaria 

 and Dermatocarpon and between Dermatocarpon and Endocarfion . 

 In the former the intermediate forms between rudimentary crustaceous 

 thallus and typical foliose thallus are wanting ; the difference be- 

 tween the thallus of Dermatocarfion and that of Endocarfon is princi- 

 pally that of size ; yet it seems evident that there must have been 

 intermediate forms. 



Key to the Genera. 

 Thallus crustaceous, often hypophloeodal. 



Spores 6-8 celled, colorless. i. Trypethelium. 



Spores 4-celled, brown. 2. Pyrenula. 



Spores many-celled. 3. Conotrema. 



Spores multilocular, colorless. 



Exosporium normal. 4. Thelotrema. 



Exosporium thick, gelatinous. 5. Gyrostomum. 



Spores simple, colorless. 



Spores medium size. 6. Verrucaria. 



Spores very large. 7. Pertusaria. 



Thallus foliose. 



Spores multilocular, colorless. 8. Dermatocarpon. 



Spores simple, colorless. 9. Eiidocarpon. 



