IOWA- ACADEMY OF SCIENCES. 
35 
ecological papers are surely more important. The titles 
for the present period number 222, or one more than half 
of the whole 443 known titles for the four periods. 
The bibliography of North American lichens published 
by Calkins in 1896 numbered 122 titles. To this the pres- 
ent writer added 101 in a paper published in 1898, making 
a total of 223 down to the date of Calkin’s paper, April, 
1896. Since then the work has gone forward till my num- 
ber is 433, including all obtainable to the present time, 
but by far the larger number of additions being from ob- 
scure places prior to 1896. Still a new title comes to light 
frequently, and the bibliography is not yet ready for pub- 
lication with this paper. Among the 443 titles, are quite 
a number concerning the lichen flora of our arctic regions, 
which have not been mentioned in this paper. While 
these are all minor papers, the number of species listed in 
them is upward of 300 and adds considerably to our knowl- 
edge of the lichens of the region. 
The facts brought out in the discussion of the present 
period show that a good deal has been accomplished in the 
few years. However, several of the workers of the period 
are still busy with their studies, and the information re- 
garding their work must be taken as in no sense final or 
complete. Also it should be stated before concluding that 
there is not an area of considerable size on the American 
continent which will not still yield lichens new to the 
region, and that our knowledge of the lichen flora as a 
whole is still quite meager. However, there is also great 
need of serious studies in the various genera, not one of 
which has yet been monographed for America. And while 
all this is true, morphology, physiology and ecology will all 
continue to furnish American workers with labor quite as 
interesting and productive of results. 
In closing it may be repeated that it is not supposed that 
the bibliography upon which this historical statement is 
based is more than approximately correct and complete; 
and it is certain that some errors of statement have been 
made, while very possibly something of real importance 
may have been omitted from the discussion. It is to be 
