GRASSES OF IOWA. 389 



Alleghanian area. This area reaches its greatest development in 



this state along the Mississippi and reaches over to the Missouri river, 

 extending farther eastward in southwestern Iowa, thence farther north 

 along the river. The representative plants are: 



Juniperus Virginiana (northward). filia Americana. 



Quercus macrocarpa . Sanguinaria Canadensis . 



Cory! us Americana . Negundo aceroides. 



Rhus glabra Ulrnus Americana. 



Primus Americana. Acer saccharinum . 



Dicentra cucullaria . Acer nigrum (Des Moines basin) . 



Solidago serotina (northward). Aster Novcc-Anglics (northward). 



Carolinian. This area reaches its greatest extension in southeastern 

 Iowa, spreading northward to Dakota, with a few representatives. The 

 representative plants are: 



Gymnocladus Canadensis . Juglans nigra . 



Morus rubra. Rhamnus lanceolaia. 



Nelumbo lutea . Vernonia Noveboracensis . 



Polygonum Pennsylvanicum . Polygonum dumetorum var. scandens . 



Martynia proboscidea . Eupatorium serotinum . 



Arid transition. This area reaches its greatest development along 

 the immediate border of the Missouri river, on the loess bluffs, but ex- 

 tends eastward to the divide between the Mississippi and Missouri rivers 

 in Carroll and Dickinson counties. Representative plants are as follows: 



Cnicus canescens . Shepherdia argentea (N.). 



Symphoricarpos occidentalis . Helianthus annuus. 



Vucca angustifolia. Helianthus l < aximi/iani . 



Petalostemon multiflorus . Gaura coccinea. 



Aplopappus spmulosus . Gaura parvitlora. 



Grindeha squarrosa. Liatris punctata. 



Euphorbia marginata . Euphorbia heterophylla. 



Hosackia Purs /liana . Lactuca pulchella. 



Erysimum asperum . Dalea laxiflora . 



Psoralea esculenta . Mentzelia ornata. 



Lygodesmia iuncea. Sporobolus cuspidatus. 



Bouteloua oligostachya. Buchloe dactyloides (N . W.) 

 Schedonnardus paniculatu* (N . W.). Oxyiropis Lai/iberti. 

 Astragalus lotiflorus var. brachypus . 



It should be observed that the ?onal boundaries of plants are not 

 sharply marked, but that the different areas contain some types of each 

 of the areas. The main features of the flora are essentially prairie. The 

 intermingling of western and eastern prairie types is most marked on the 

 loess bluffs. 



ECOLOGICAL DISTRIBUTION. 



Mr. Whitford, 1 who has made a study of the forests of northern 

 Michigan, considers the forests under the subject of climatic, ecological 



♦Life Zones and Crop Zones of the United States. Div. Biol. Surv. U. 8. Dept. Agrl. 

 10. Yearbook U. 3. Dept. Agrl. 1897:115. 1894:203-214. 

 1. Bot. Gaz. 31: 291. 



