THE NATURE AND CLASSIFICATION OF 
LICHENS— II. THE LICHEN AND ITS 
ALGAL HOST' 
Bruce Fink 
The writer had no thought, in addressing the questionnaire to 
botanists three years ago, of attempting to settle thus the classifi- 
cation of lichens. It was thought rather that the views of leading 
botanists would be valuable, and also that the problems involved 
could be treated more intelligently after current opinion and the 
arguments back of it were known. As stated in the first paper of 
this series, the writer has reserved his own ideas for this paper 
and another to follow in the series. Since his viezvs regarding 
lichens are not those held by most persons zvho have zvorked on 
these plants, the phraseology used, even in the discussions of 
researches, must be somezvhat different from that found in the 
papers cited. If the facts appear, to those zuhose zvritings are 
considered, to be distorted, careful analysis zvill probably shozo 
that there is no other distortion than that necessarily involved in 
treatment under a different conception of the nature of the lichen. 
The Presence of Algae in Lichens Established 
For centuries lichens and the algae which grow with them were 
thought to be genetically related. Walroth (137), in the first 
account of the green cells in lichens, noted their resemblance to 
certain algae. Elias Fries (60), Kiitzing (78), Koerber (73, 74), 
Nageli (93), Thwaites (129), Thuret (128), Tulasne (136) and 
Itzigsohn (68) renewed the observations of Wallroth. Some of 
these and others as Sachs (108), Hicks (67), Nylander (95, 96), 
Krempelhuber (76), Muller (91) and Arcangeli (2) thought that 
the algae were the primordia of certain lichens or other stages in 
their development. Several observers as Bayrhoffer (18), Mul- 
ler (90, 92), Th. M. Fries (61), Archer (3), Arcangeli (2), 
’ Contributions from the Botanical Laboratory of Miami University — X. 
97 
