Fink: Classification of Lichens 
155 
silicate inhabiting lichens, which are mainly epilithic, are poorly 
developed, while their algal host is strongly developed. Lichens 
that grow in the calciferous rocks are strongly developed, and the 
algal host cells are not abundant. This favors the view that the 
more intimate the relation of the lichen to the rock, the less its 
dependence upon an algal host. This again favors the conclu- 
sion that the oil is a reserve product and accords with our find- 
ing that, in bark-dwelling lichens, the closer the relation to the 
substratum the less intimate that with the algal host. Fiinfstiick 
(63) found that the more abundant the algal host cells, the less 
the amount of oil present; and this, with his other findings given 
above, makes our conclusion practically certain. 
It may seem that we have gone far afield in discussing at some 
length the relation of the lichen to its algal host and to the sub- 
stratum. For the writer and some others, this would not have 
been necessary in the present series of papers, for some of us 
believe that the lichen is a fungus, whatever its relation to the 
algal host. But for others, the traditions would not be aban- 
doned without proving that the lichen is a parasite, or perhaps 
partly a saprophyte as well, on the alga. As stated above, it will 
be seen that the relation of the lichen to the algal host can not be 
understood until we also have before us the facts regarding its 
relation with various substrata. Hence, we have given a sum- 
mary of knowledge on these points and are ready to treat, in the 
next paper, the classification of lichens, with the matter of their 
nature thoroughly considered. 
SuMAIARY AND CONCLUSIONS 
1. There has been hitherto no agreement regarding the nature 
of the lichen, and the only thing about the problem generally be- 
lieved by botanists is that the green and the blue-green cells in 
lichens are algae. 
2. Due probably to clinging to traditional phraseology, most 
botanists are not able to express themselves consistently with re- 
spect to any view that they may hold relative to the nature and 
the proper treatment of lichens. 
3. The text-book statements about lichens are rarely coherent, 
excepting those that cling to an entirely traditional and erroneous 
position. 
