PLATE 27. 

 UMBILICARIA PUSTULATA (L.) Hoffm. 



i. Portion of thallus natural size^ a, apothecia ; b, pustules. 

 2 and 3. Section through apothecial branch and thallus. 



4. Paraphysis and apothecium with immature spore. 



5. Spores; a, spore before the formation of septa has begun; b, later 

 stage ; c, mature spore. 



6. Algae and enclosing hyphae (haustoria). 



Family 4. GRAPHIDACEAE. 



There is Httle difficulty in recognizing the limitations of this 

 family ; but at first it will seem doubtful as to the position it should 

 be given in the sequence of families ; judging from the representa- 

 tives occurring in our territory it would seem that this formed the 

 lowest family in the series. But if we include Rocella it at once re- 

 ceives a high position in the series. For a long time I was in doubt 

 as to the true position of this genus, but finally came to the same 

 conclusion as Reinke and consider it as a lecideine type, as is indi- 

 cated by its apothecial characters. There are, however, some 

 serious objections to such a conclusion. First, as to the dark hy- 

 pothecium of Rocclla, it may be stated that this does not indicate an 

 unmistakable lecideine type, since we have a number of genera 

 among the Lecideaceae with colorless hypothecia ; furthermore Pyx- 

 ine is recognized by its dark hypothecium, though it evidently 

 does not belong to the family. Another objection to placing Ro- 

 cella with the Graphidaceae is the form of the apothecia ; they are 

 typically discoid and not irregular or linear ; it must, however, be 

 admitted that the most suitable position at present is among the 

 Graphidaceae and it is this consideration which determines the posi- 

 tion of the family here adopted. 



The representatives of the family, as far as they occur in the ter- 

 ritory, are characterized as follows : The thallus is crustaceous, very 

 rudimentary, and for the most part hypophloeodal ; the symbiotic 

 algae are mostly Chroolepus. 



The generic groups indicate a polyphyletic origin, but it can only 

 be stated in a general way that the ancestral forms of the fungal 

 symbionts are derived from the Phacidiaceae (plate 5), as is evi- 

 dent from the apothecial, as well as the spore-characters ; the fungal 

 ancestor of Graphis was doubtless derived from the genus Hyste- 

 riuni. 



