80 THE VEGETATION OF THE UNITED STATES. 



extending as far as Pennsylvania and Florida, with the suspicion of 

 its having been introduced along its easternmost limit. Solidago is 

 closely confined to the Grassland and Grassland-Deciduous Transition 

 area, with a northwestward extension in regions of this type through 

 southern Idaho and eastern Washington. Gutierrezia is found in the 

 western portion of the Grassland and in the higher portions of all areas 

 in the extreme southwestern portion of the country. In addition to 

 its natural habitats, this plant is an extremely common one in all 

 areas in which the original cover of grasses has been disturbed by 

 grazing or other unnatural conditions. 



14. Characteristic Grasses of the Great Plains and the Prairies. 



(Plates 11 and 25.) 



Bouteloua oligostachya (Nutt.) Torr. 



Bulbilis dactyloides (Nutt.) Raf. ( = Buchl6e dactyloides Nutt.). 



Kceleria cristata (L.) Pers. 



Agropyron spicatum (Pursh) Rydb. ( = A. divergens Nees, = Festuca spicata 



Pursh. Not A. spicatum Scribn. and Smith). 

 Hilaria jamesii (Torr.) Benth. 

 Andropogon virginicus L. 

 Bouteloua hirsuta Lag. 



Four of the members of this group of grasses characteristic of the 

 Grassland and Grassland-Deciduous Forest Transition regions have 

 already been used in constructing the map of cumulative occurrence 

 of grasses (plate 1 2) . The ranges of three other species are given in plate 

 25. Agropyron and its allies have been selected because of their 

 importance in the formation of the Grassland of the northwestern 

 States, Hilaria because of its importance in the southernmost exten- 

 sion of the Grassland and the Desert-Grassland Transition, and Andro- 

 pogon because of its importance in the easternmost portion of the 

 prairies of the Grassland-Deciduous Forest Transition. 



15. Palustrine Herbaceous Plants. (Plates 26 and 27.) 



Sparganium americanum Nutt. (including S. americanum var. androcladum 



(Engelm.) Fern, and Eames). 

 Dianthera americana L. 

 Sium cicutsefolium Gmel. 



These palustrine herbaceous plants are of interest for the same reason 

 that has been mentioned in connection with palustrine shrubs. Spar- 

 ganium is extensively distributed in the Eastern States, but its pre- 

 cise range is not well known. Dianthera is found in the eastern half 

 of the United States south of Wisconsin and outside the eastern half 

 of the Coastal Plain. Sium is found practically throughout the United 

 States, with the exception of the continental desert areas, its occur- 

 rence throughout a large part of this region being extremely infrequent. 



