192 



the 1) western .species, three, starred in the folldwiiiK list, are 

 practically confined to the sand region. 



Ath('i'p(i<i<iii ciii't'i i><'ii(J III UK I'til ijl It'll 'hi XiiHiiIIii 



* IVili II inti riiiiiis/ii'riii II III XkIuiIux aspir 



* Kl'l/K/iii mil II rkii iiKii II II III IldiUiiilii ihhihiUi 



liilics iiiinKiiN rleiiKC * Ai'ti'iiitxiti <-ii inlntn 

 Prfillnxfi'iiiiili i-diiilltliis 



A comparison of the vegetation of the Illinois River valley 

 sand region with that of the dunes along Lake Michigan is of 

 interest on account of the short distance between the two re- 

 gions. P]xcepting the temperature, the difference in the eco- 

 logical conditions is scarcely sufficient to cause a wide varia- 

 tion in the floras. The tlunes of Lake Michigan, however, are 

 e.ssentially a beach forniation. and the vegetation as described 

 by Oowles ( "i)*J ) shows but slight relationships with the western 

 prairies. On the beach proper only eight species occur which 

 are common to the two dune areas, and three of these. Arteml- 

 siii ciniilufti. ( 'ii/iniiiiri/fii /(ii/i/ifo/iii. and Lif/insjimtiiini (iniclnii. 

 are western in their range. The flora of the shifting dunes 

 shows scarcely more similarity. In the established dunes the 

 resemblances are stronger. Six species of the basswood dunes 

 and nearly all those of the oak dunes are found also in the 

 inland region, and Cowles's list includes (Jucrciis rchititm. Rhus 

 iifiiiiKififd.Cniri-ii rin/l)ii(niii, (' t/penis Schirriiiitzii, Opiiiifiti hniiii- 

 fiisd. (Kiinfln'rii r/ioiii/iijirfiiiii, Moiidnlii jiinirfiifii, and other spe- 

 cies abundant on the sand along the Illinois River. In both 

 localities these plants belong principally to the derived element; 

 and as the adjacent forests are of the same type in both regions 

 it is to be expected that the same species would be able to 

 adapt themselves to the sand. It is in the endemic element 

 that the greatest contrast lies. The dunes of Lake Michigan 

 have no ('r/sfdfr//d, Krai/rosfis iriclioilcs. Bodfi'lmid, Ainhfusid 

 lisildstdcJiijd. FnicUcliid, Enphorhid Gri/rri, ('dlHrrliiii\ or Clir//- 

 supsis, all characteristic of the inland regicni; while the latter 

 lacks ('dl:ih' (iitwricinid. ('iirispcrnidtn hi/ssitjiifh/iinii, Eiip/iorhia 

 pill ippiiiifiilid , Ldl/ii/nis iiidriliiiids. Ainiiiiiphild umidrid. and 



