THE LICHENS OF “ THE LEDGES/’ BOONE COUNTY, 
IOWA. 
BY KATY A. MILLER. 
The study of the flora of “ The Ledges ” furnishes much 
opportunity for interesting research. Besides possessing 
sdme of the most beautiful scenery of Iowa these ledges, 
with their moisture and shade, make an inviting habitat 
for plants of many kinds. Of these plants the lichen flora 
is perhaps the most interesting, because heretofore little 
work has been done on the flora of perpendicular sandstone 
exposures, such as are here presented. 
“The Ledges” are of ferrugenous sandstone, rising in 
some places to a height of seventy-five feet. They present 
an almost perpendicularly exposed wall for about two miles 
along the Peese creek, a tributary of the Des Moines river. 
Disintegration seems to have gone on slowly, for many 
crustose thalli are well developed. In places where disin- 
tegration has gone on to any extent the refuse falls to the 
water below, so Cladonias are found only on the sandstone 
of the exposed faces and are comparatively rare. Such 
tree forms as Parmelias, Fhysias and Ramalinas were 
found on the sandstone, and such a typical tree form as 
TJsnea harbata w T as collected only from the sandstone. 
These occurrences are explained by the nearness of trees 
from which these forms have migrated, and which afford 
abundant shade and moisture for them. 
The study of these lichens has well repaid us, as several 
species new to Iowa were found, these being Acarospora 
(. Lecanora ) cervina var. oligocarpa, Verrucaria viridula , Bil - 
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