222 NATUEAL HISTORY BULLETIN 



Certain other species are listed as appearing both on the sand- 

 dunes and on some of the dry prairie areas, but they also show 

 a more or less decided preference for sandy areas. They are 

 the following: 



Carex cephalophora Muell. 



Cenchrus carolinianus Walt. 



Crotalaria sagittalis L. 



Oenothera rhombipetala Nutt. 



Polygonum tenue Michx. 



Strophostyles pauciflora (Benth.) S. Wats. 



Tephrosla virginiana L. 



Tradescantia reflexa Raf. 



Viola pedata L. 



To the foregoing list should be added Amaranthus blitoides 

 Wats., and Cycloloma at riplici folium (Spreng.) Coult. The for- 

 mer species occurs in dry places, but in our region appears to be 

 most common in sandy places. The latter species is usually 

 found in sandy places and occurs on both the dune areas, but in 

 the western part of Iowa and the adjacent territory it is found, in 

 common with most of the other species of the last list, on the dry 

 prairie loess ridges. This apparent variation in the habitat of 

 species of this list is not as great as it appears at first sight, for 

 not only are these loess-covered areas xerophytic, but the loess is 

 porous and consists in large part, sometimes more than 70 per 

 cent, of (quartz) sand-dust. 



Heliantlius pefiolarls Nutt. is also common at Muscatine, and 

 is also found in the dry, western part of the state. 



Still other species of our general territory, Avhich habitually 

 appear upon sandy areas and only exceptionally upon other dry 

 areas (though none have been found in the particular prairie 

 areas other than dune areas considered in the table), and which 

 are not included in the table of plants, should be added. They 

 are the following : 



On the Harrison county dunes : 



Desmodium canescens (L) DC. 

 On the Muscatine and Louisa county dunes: 



Androsace occidentalis Pursh. 



Aster linariifollus L. 



Aster oblongifolius var. rigidulus Gray 



Commelina virginica L. 



