IS'.I 

 I/chimt/iDs xt rii iiiosnx \,. 



t 'o/'i'llJIX/X jXlhlKltll Nlltt. 



Af/iillfii MiUit'orniiii 1,. 

 Aricni'iKKi riiiiildt)! MicllX. 

 Mcsadi'ii'ni of r( pi ic'ifal'iK (L.I Haf. 



PHVTOOEOaRAPHICAL RELATIONSHIPS OK THE FlORA. 



A casual inspection of the pi'ecetiinji- list of species, ISS in 

 numl)er, will show the presence in the sand vegetation of nu- 

 merous plants of western distrihution. Sdnu' of these occur in 

 Illinois only in the sand reg'ions. so far as known, and others 

 are of limited range in various parts of the state. In order to 

 study more carefully this western relationship the Hoia has heen 

 divided into two groups, iuclu lin.;-. first, tho-;e species living 

 in the prairie formation, and, second, those found (uily in the 

 lilack-ja(d\ forest. It is believed that this sejiaration will dis- 

 tinguish the older and more jji-imitive flora, inh-ahiting the old- 

 er plant-formation, from the younger and more recent flora, 

 occupying the younger formation, and doulitless derived to a 

 large extent from the vegetation of the surrounding woodlands 

 and prairies. It has heen mentioned that nearly all the species 

 of the sand prairie grow also in the lilack-jack, and that their 

 presence there is prol:)ai)ly due frequently to persistence through 

 the changed ecological conditions. It is also evident that many 

 of the more recent .«<pecies have penetrated into the bunch- 

 grass prairies and are now mingled with the endemic element 

 there. A third and minor group of five species has not been 

 included in this division, since its meujiiers occur only on the 

 fi'ont of dunes which have invaded natural groves on the Miami 

 loam, and are undoubtedly derived directly from the vegetation 

 of that soil. These ^ve Clciiiufis Shush, i'.iijihiirhid /ictcroji/ii/l/d. 

 Sicijds iiiHiiihitiis. StildiiHiii ddjnnd. and / li n-iisl m m il i ra iicdl ii ni . 



The vegetation of Illinois, with the possible e.\ce|>tion of 

 the extreme southern part, lias been de\eloped since the close 

 of the glacial period. Postglacial migratidu inio the state has 



light green, short- petioled leaven which are nearly erect in a basal cluster, whili; in 

 fffWf()(//(i« )7/i/)oi/(.s-(.s they are darker green, more or le>s spreailing and .scattered on 

 the stem.— Ohio Naturalist, Vol. \'. i|!i04i, \k L'14. 



