forest species, but usually blends most completely with the 

 prairie flora. 



The beaches of the Okoboji lakes and Spirit lake frequently 

 show the intergradation of swamp and beach. On the newer 

 parts which are subject to wave-wash, there is often a blending 

 of low-ground or swamp species with those which habitually 

 grow in moist, sandy places. 



These species are marked ''w" in the list, and those which 

 were found on lake beaches are indicated in column I. Of the 

 species so marked in this locality list, Verbena hastata, Stachys 

 palustris, Erigeron philadelphicum and Ambrosia trifida are not 

 uncommon on higher prairie. 



A similar mingling of hydrophytic forms is noticeable in the 

 Harrison county dune region, where pools and low, wet places 

 are not unusual. The hydrophytic species which here appear on 

 wet sand, and which mingle more or less with the ordinary sand- 

 xerophytes, are also marked ''w" and appear in column V of 

 the plant-list. 



The bars and sandy shores of streams also frequently show a 

 number of these hydrophytic forms. Columns II and III of the 

 plant-list contain such species, marked *'w." The species of 

 Eragrostis and Hemicarpha are very commonly the pioneers on 

 river-bars. 



A few species which usually occur in forested regions are also 

 found on the lake beaches and river bars. They are marked 

 ^'f" in the list. 



The most common species which occur on the beaches and 

 bars, especially where the vegetation has become quite w^ell 

 established, are prairie species. Sporobolus cryptandrus, Cy- 

 perus Schweinitzii, Corydalis micra^itha, both species of Polan- 

 isia, Strophostyles helvola, and Euphorbia glyptosperma are the 

 only species restricted to the sands of the lake beaches. Even 

 Cenchrus, and Strophostyles pauci\fforiis are not restricted to 

 sand, but often occur on the upland prairies of the western part 

 of the state. All other species are essentially prairie species. 



The true sand-species of the river bars are the same as those of 

 the lake beaches, excepting that the Euphorbia has not yet been 

 found on the former, which, however, contain the following ad- 

 ditional speeies: 



The several species of Eragrostis, commonly in wet places; 



9 



