1 9( I 



proceeded from three principal centers or zones: the Austro- 

 riparian zone or Coastal plain, a U-shaped area lying along the 

 Atlantic and (lulf coasts and the lower Mississippi valley: 

 a sontheastern center lying within the V, and a southwestern 

 one lying to the west of it. The last two centers have furnished 

 most of the plants of the sand region and, indeed, of Illinois as 

 a whole, and the floral elements from them will l)e spoken of 

 as the Atlantic and the Sonoran elements respectively. A 

 northern extension of the Sonoran element has occupied the 

 inland territory designated by Engler as the Prairie province, 

 and an eastern arm of tiiis province reaches across northern 

 Illinois into Indiana. This is shown by Pound and Clements on 

 their map of the Prairie province ("98, '00). This arm is almost 

 surrounded on the north, east, and south by the Atlantic prov- 

 ince, and it is also intersected along the streams liy In'oad or 

 narrow strips of woodland, re[)resenting the same province. 

 When we consider also the fact that in Illinois the forests are 

 climatic and the prairies edaphic. it is not surprising that the 

 Sonoran floral element in the Illinois prairies is obscured by 

 the presence of a large number of species of the Atlantic ele- 

 ment derived from the adjacent forests. 



Of the 117 species growing on the prairie formation of the 

 sand region 34, or 29 percent, are of typically western range, 

 that is, from Illinois w^est across Nebi'aska and thence south in- 

 to Texas, a distribution in many cases practically coincident 

 with the Prairie province and clearly indicative of their Sono- 

 ran origin. These are as follows: 



* 



Eipi'isctinii roh 11x1 II III Pcfdloxfpmon piirpvrciiK 



Sf/'jxi Kparliii *Eiipli(irh'ia (ieijvr'i 



* ('iihiiiiiii'il til liiiiij ifiil Id * ( 'ii 1 1 1 rrlioi' t rill III/ iiliitii 

 * Iliiiitiliiini /lirsiitii * Ojiiiiitiii li II iiiit HSU 



* Kriii/foxt IX t I'ir/iiiili's * (Emit lirrii rlioiiih'i pi'tiilii 

 ' Ci/ju-i'iix Sell Hwiiiifzii Asrlepiax Sull i ruiitii 

 *('i/jirriix Hiislii'i Lilhoxpenini III (jniclini 

 ('iiri'.r i/rii mill Lit/ioxpcriii mil Unearifol i ii m 



* 



( ' ijchiliiiiiii iii n pi ir'itii] I II III \ I' rill' II II str'irtd 



* Eroi'l irli HI i-ii III pi'sfr'ix Vrrheiia hrurfeoxa 



