72 
IOWA ACADEMY OP SCIENCES. 
6. The action was probably not simultaneous over the entire 
area, the fine material removed from the most barren parts 
being deposited in places already prepared for its retention. 
THE FLORA OP THE SIOUX QUARTZITE IN IOWA. 
BY B. SHIMEK. 
The Sioux quartzite is exposed in this state only in the 
extreme northwestern corner of Lyon county. Other and 
greater exposures however are found in the adjacent parts of 
South Dakota. 
The chief exposure on the Iowa side is located only a few 
rods south of the state line and about one and three-quarters 
miles east of the Big Sioux river. 
It occupies a depression in the rolling prairie, which is 
bordered by hills on the north, east and south, and slopes 
gradually to the Big Sioux bottoms to the west. It is best 
seen at and near the junction of two streamlets, one coming 
from the east and the other from the south, the course of the 
resulting stream being westward. 
At the time that the observations herein recorded were made 
(August 4 and 6, 1896), these streamlets were almost dry, there 
being only a. few disconnected pools of water. 
The greater portion of the exposure is horizontal, vertical 
ledges not exceeding six feet in thickness being found only 
along the streamlets for a few rods above their juncture. 
The exposure is in part barely disguised by a scant surface 
soil upon which, and upon the bare rock, flourishes a flora in 
some respects unique, and strikingly different from that of the 
surrounding prairie, a fact already noted by Prof. J. C. Arthur, 
who in the “Contributions to the Flora of Iowa,” No. VI.,* 
says: “The extreme northwestern corner (of Iowa) is geolog- 
ically and botanically very unlike the rest of the state.” 
The list of plants herein given is undoubtedly far from com- 
plete, being the result of a rather hasty survey. It shows a 
flora which is sufficiently unique, however, to be of interest to 
the student of plant distribution. 
* Proc. Davenport Acad. Sci., vol. IV., p. 73. 
