202 



globose terminal apothecia it has been thought to be a near relative 

 to Sfhaero-phorus. Both conjectures are wide of the mark. 



The thallus is minute, dark in color, dichotomously branched 

 and very rigid when dry. The greater bulk of the structure consists 

 of the hyphae which extend longitudinally in the central portion of 

 the thallus-branches, but describe a trajectory outward near the sides. 

 The arrangement of the tissues is typically radial. There is no 

 cortical tissue ; the hyphal projections and branches nearest the outer 

 surface undergo a change whereby they serve as a protective cov- 

 ering, more especially intended to prevent excessive evapora- 

 tion of moisture. Next to this incipient tegument lies the algal 

 layer ; the algae, which are Rivularia nitida, occur in chains lying 

 parallel with the curved or diagonally inclined hyphae ; it was impos- 

 sible to observe whether they extend beyond the surface or not, al- 

 though this is affirmed by some authors. The hyphae do not form 

 haustoria about the algae ; they simply extend through the gelatin- 

 ous covering or lie in contact with them. There are no algae in 

 the central hyphal portion of the thallus, nor do they extend quite to 

 the apex. 



The apothecia are small, globose and terminal, appearing as small 

 nodular enlargements on the ends of the branches. At first the 

 apothecium is entirely enclosed by the terminal portion of the thal- 

 lus, but finally an apical pore is formed which may increase to a con- 

 siderable size. The epithecium is dark, of about the same color as 

 the thallus. The paraphyses are long and slender, the spore-sacs 

 cylindrical, with eight colorless simple elliptical spores in one row. 

 The hypothecium is colorless and consists of a hyphal network. 



Only a few species are known, which grow upon rocks in moist 

 places ; they seems to occur in the temperate and tropical zones as 

 well as in the far north. 



PLATE 66. 



Lichina confinis (Muell.) Ag. 



i. Natural size. 



2. Terminal portion of thallus with apothecia, magnified. 



3. Section of apothecium. 



4. Section of thallus. 



5. Paraphyses and spore-sac. 



6. Spores. 



7. Algae. 



