THE HISTORY OF LICHENOLOGY. 13 



Within comparatively recent years there have been 

 numerous investigators who have made a special study 

 of the relationship of fungus and alga as they occur in 

 a lichen. We cannot cite authors nor enter into any 

 discussion of the results obtained. 



The general conclusions may be summarized as fol- 

 lows : 



1. Certain algae, mostly of the simpler Chlorophy- 

 ceae and Cyanophyceae have entered into an intimate 

 biological relationship with certain fungi mostly de- 

 rived from the Ascomycetes (sac-fungi). 



2. A lichen is represented by a fungal portion and 

 an algal portion. The two parts enter into a sym- 

 biotic relationship which is of such a nature that both 

 are very materially benefited. The two organisms 

 are complementary to each other, one supplies what 

 the other lacks. 



3. The fungal portion cannot exist independently, 

 while the algal portion can. 



4. The algal types are fairly well known. They 

 are (1) Cystococcus humicola which occurs in the 

 majority of lichens ; (2) Pleurococcus vulgaris ; (3) 

 Exococcus ; (4) Glceocapsa ; (5) Chroococcus ; (6) 

 Nostoc ; (7) Stigonema; (8) Chroolepus ; (9) Con- 

 fervacece. 



Bornet, Baranetzky, Famintzin and Woronin are 

 among those whose efforts have aided in giving us a 

 more exact knowledge of lichens. Jumelle (1892) is 

 perhaps the first who has entered into a careful study 

 of the carbon-assimilating function of lichens. Reinke 

 (1894-1896) after considerable study came to the 



