14 GUIDE TO THE STUDY OF LICHENS. 



conclusion that lichens shotild be considered as a dis- 

 tinct class. According to this author a lichen is as 

 much a morphological unit as a fern or an oak. A 

 lichen is not a fungus parasitic upon algae. He has 

 shown that the existence of the lichen is dependent 

 upon the relationship of the fungal portion and the 

 algal portion. Separating the two destroys the lichen. 

 Lindau (1895) objects to Reinke's views and agrees 

 with Schwendener. Darbishire (1897) is a strong 

 supporter of Reinke. He has also made a careful 

 study of the soredia (soralia) as they occur in the 

 Pertusarias. As for myself I favor Reinke's view as 

 will be explained more fully later. 



Thus concluding the historical review with the be- 

 ginning of the year 1897, we find the status of our 

 knowledge of lichens somewhat as follows : 



1. Schwendener's theory of the dual nature of 

 lichens is quite universally accepted as correct. That 

 is, a lichen consists of a fungal and an algal por- 

 tion. 



2. Reinke's theory of the autonomy of lichens is 

 beginning to receive general recognition. According 

 to this view a lichen is not a fungus parasitic upon 

 algae. The mutual interdependence of the fungus and 

 alga is so great that in many instances neither can 

 exist alone. 



3. Lichens doubtless form a distinct class equal in 

 systematic importance to mosses, fungi, liverworts, 

 etc. 



From this historical review we learn that lichenol- 

 ogy has had a very checkered career and that the ad- 



