28 IOWA ACADEMY OF SCIENCES. 



THE FLORA OF THE SIOUX QUARTZITE IN IOWA. 



BY B. SHIMEK. 



II. 



5 



A further study of the flora of this restricted exposure dur- 

 ing the third and fourth weeks of last June offered certain sug- 

 gestions upon geographical distribution which are here briefly 

 presented. 



In addition to the area described in the first paper on this 

 flora (1. c. p. 72; a second exposure was examined. This lies 

 near the Big Sioux river, nearly two miles west of the first 

 exposure, and extends quite to the state line. It resembles the 

 first exposure, but its surface is more broken, and also much 

 greater in area. Near the central part there is a deep depres- 

 sion, occupied in part by a large pond. This exposure is like- 

 wise chiefly horizontal, but around the central depression, and 

 also on the sides nearest the Big Sioux river, vertical sections 

 are prominent, those at the latter point being fifteen to twenty 

 feet high. Near their base there is an accumulation of soil 

 which gradually runs out into the narrow alluvial valley of the 

 Big Sioux river. 



At the base of the lower ledges in the first exposure similar 

 richer soil is found bordering small pools, which are connected 

 only during flood periods. 



Upon this soil at both points, but chiefly at the former, was 

 found a flora similar (in so far as it is developed) to the flora of 

 the more easterly portions of the state, and to the floras of our 

 river courses. The species, which are enumerated in Table I, 

 are all common and well known eastward. 



Within a few feet, upon the exposed or scantily covered 

 rock, were abundant specimens of the plants, which in that 

 region at least, are peculiar to the rock exposures. In addition 



*The first paper on this flora appeared in the Proc. la. Acad. Sci., Vol. II, pp. 78-77. 



