IOWA ACADEMY OF SCIENCES. 
15 
Early in the nineteenth century, monographs of genera 
began to appear in Europe, and after the first quarter of 
the century, European lichenists of note became so numer- 
ous that we can mention only a few of them in passing. 
Wallroth, Korber, Massalonge and Nylander, each in turn 
did much for systematic lichenology in Europe during the 
century just closed and helped directly or indirectly in our 
studies as well, while perhaps Elias Fries, through his in- 
fluence upon Tuckerman, impressed himself upon Amer- 
ican lichenology more than any one of them. Arnold, 
Stizenberger and Muller also aided greatly in the closing 
years of the last century, and Wainie, Zahlbruckner and 
Hedlund are among the Europeans who have, in the pres- 
ent century, aided effectually in our work. 
Wallroth did good work for his day in the morphology 
and physiology of lichens, and other European workers in 
these fields have profoundly influenced our American 
thought and must be mentioned. About the middle of the 
last century appeared works by DeBary and Schwendener, 
which were the beginning of a revolution in ideas regard- 
ing the nature of lichens. DeBary detected the close 
relationship between the lichens and the algae on one side 
and the fungi on the other, and Schwendener, at first hostile 
to the views of De Bary, in 1868 announced his belief that 
the sp-called gonidia and gonimia were really algae grow- 
ing under peculiar conditions. He set to work to study the 
algal types occurring in lichen thalli, and received credit 
for establishing the now generally accepted view as to the 
dual nature of lichens. The fungal portion of the lichen 
commonly gives form to the plant, or colony, and produces 
the spores, and American as well as European writers of 
text-books soon began to follow De Bary and Schwendener, 
placing the lichens among the fungi. The older systematic 
lichenists of two continents were almost violently hostile 
to the new theory, and many of the younger and better 
trained lichenists and botanists, who accept the newer 
views as well established, have not felt so certain that the 
distribution of lichens among fungi is at all a final disposi- 
tion. Finally, Reinke, in a paper already mentioned, and 
