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 Collema 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 Col/ema, Leptogium, 
Hydrothyria, Peltigera. ft Stictina is derived from Peltigera, 
Sticta, which is evidently S#ctina 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 uliginosa, Thelidium minu- 
tulum, 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 Cuscuta 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. Asa 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. 
