156 



The Plant World. 



in Iowa, except that it is more abundant in the prairie region than 

 in a country broken up with timber. 



If we go northward through the prairie region of Minnesota 

 into Manitoba, the same types of plants occur. Near Winnipeg 

 the Aster midtiflorus, A. laevis, Solidago rigida, S. missouriensis, 

 Psoralea argophylla, P. esculenia, Silphium laciniatum are much 

 the same as on our Iowa prairies. The grasses like Panicum 

 virgatum, Andropogon provincialis, A. scoparius are common 



Fig. 1. Xerophytic vegetation. Tctradymia Nuiiallii, a spinescent com- 

 posite shrub, and greasewood, Green River County, Wyoming. 



and m.uch like our Iowa plants. The Helianthus Maximiliani, 

 common in northwestern Iowa, extending eastward to the Mis- 

 sissippi in northern Iowa and southern Minnesota, is, however, 

 not common along the Mississippi in Iowa or southeastern Min- 

 nesota. It is a much more common species in Manitoba than 

 the H. grosseserratus. It, like all other plants, is smaller in 

 Manitoba than in Iowa. As we go west from central Iowa the 

 prairie country is broken up by numerous small ponds contain- 



I 



