THE VEGETATION OF THE TOWN PRAIRIE HU SAC. 
HERMAN FREDERICK LUEDERS. 
Having during the past twenty years been a witness of the 
rapidity with which the original boundaries of the distribution 
of our native vegetation were obliterated, and many formerly 
abundant species almost destroyed, I concluded to employ a 
period of enforced partial idleness in obtaining the material for 
a detailed record of the distribution of the native vegetation of 
my native county of Sauk. 
It is a fragment of this only partly completed work which 
I here present. 
Long continued and intimate acquaintance with the vegeta¬ 
tion of the town of Prairie du Sac, had convinced me that the 
dependence of vegetation on the geological and topographical 
features of the country received there an unusually forcible ex¬ 
pression on account of the number of distinct vegetative groups 
that presented themselves. 
The accompanying map, Plate XVII, is a hasty attempt to re¬ 
trace the boundaries of these groups as they appeared before 
invaded by axe and plow. 
A few words on the geological surface features of Sauk county 
may aid in correlating the geology of the town of Prairie du 
Sac with that of southwest Wisconsin in general. Bounded on 
the east and south by the Wisconsin river, Sauk county in¬ 
cludes in the northern part the most extensive outcrop of Ar¬ 
chaean rock possessed by this state, the quartzite of the Baraboo 
bluffs forming the axis or core of its rocky foundation. Aris¬ 
ing near the eastern boundary and extending in a west-north¬ 
west direction through several townships, these bluffs are 
flanked on both sides by unconformably superposed Potsdam 
sandstone, which in many localities gives evidence of its ances¬ 
try and littoral origin by including pebbles and angular frag¬ 
ments of quartzite, or by passing locally into a quartzite con- 
