98 THE AMERICAN BOTANIST 



and the surface becomes hard and dry. Even the swamps 

 that in spring seemed impassible at any time of the year now 

 afford a firm footing- and allow the botanizer to explore their 

 inmost recesses. The rays of the summer sun beat upon the 

 plain with relentless force and the rising air creates lively 

 breezes that call still further for the moisture that the plants 

 find none too abundant in the stubborn soil. Only plants 

 that can endure being half drowned in spring, baked and dried 

 in summer, and frozen in winter can survive long on the Chi- 

 cago plain. 



The type of vegetation that has resulted from such con- 

 ditions is a very characteristic one. Nearly all are perennials 

 with stout tap-roots extending deep into the soil and coarse 

 stems and leaves, the latter often leathery in texture, covered 

 with hairs wax or other protection against complete desseca- 

 tion. Those that do not possess taproots, usually have some 

 sort of underground stem, from which the upright stems 

 arises. No shrubs are found. 



At first glance the plant covering may appear nearly uni- 

 form, but a little investigation shows that there are two 

 groups. These the ecologist recognizes as the high prairie 

 and low prairie associations, respectively. The high prairie 

 types occupy the crests of the low swells, especially where the 

 soil inclines to be sandy, and thus approach desert and sand 

 barren types of vegetation. The low prairie types are found 

 in richer soil where the swampy areas merge into drier ground. 

 There are, to be sure, plants common to both regions, just 

 as some weeds can thrive both in cultivated fields and waste 

 land, but enough species are found in a single area, only, to 

 cause a decided difference in the appearance of the two groups. 

 Often in the course of a few hundred feet, the observer may 

 thus pass from one fairly distinct flora to another without any 

 very noticeable change in the physical surroundings. 



In regions where the conditions of life are hard — on moun- 



