447 



processes the developing spores of gelatinous lichens acquired the 

 ability to enter into a mutually symbiotic union with other algae. 

 A series phylogenetically derived from Collcma may have 

 taken an upward course, that is, proceeded from the lower 

 to the higher, from the simpler to the more complex. As 

 an example we may cite the natural series Collema, Leptogiiun, 

 Hydrothyria, Pdtigera. If Stictina is derived from Peltigera, 

 Sticta, which is evidently Stictina with bright green algae, 

 would also be included in the series. Every phylogenetically 

 derived lichen-type constituted the beginning of a new series 

 ■which may have proceeded upward or downward; that is in the 

 direction of either higher or lower forms. In certain cases 

 it is difficult to decide whether given lichens form the beginnings 

 of a series or whether they are degenerate forms. Among such 

 doubtful forms are included Biatora nliginosa, TJielidiiun mimi- 

 Mlum, and species of Buellia and Arthonia. Many of these plants 

 live parasitically upon other lichens, and no doubt bear a relation to 

 these similar to the relation of Cusciita and Monotropa to the 

 chlorophyll-bearing genera of the same family. The above sum- 

 mary leads to the conclusion that there is a natural system of 

 lichens distinct from that of fungi. 



The author deplores the pernicious effect of Schwendener's plan 

 of the arrangement of lichens. As a result lichens received only 

 casual mention in an appendix to the different groups of lichens. 

 Lichenologists (systematic) in general have strongly opposed 

 Schwendener's plan of classification. Although Reinke has 

 always sympathized with these lichenologists, yet he regrets 

 very much that they should have made their special attack upon 

 Schwendener's theory of the dual nature of lichens. 



The following is a brief summary of the leading items discussed 

 in this paper : 



1. The true relation of fungus and alga in the lichen-thallus 

 was first pointed out by Reinke. 



2. The term Consortism antedates the term Symbiosis. 



3. Schwendener's (De Bary's) theory of the dual nature of 

 lichens is fully accepted. 



4. Most of the algal types occurring in lichens have been 

 specifically determined. The fungal types no longer exist (at 

 least in most cases) and can therefore not be determined. 



