PAPERS OX BIOLOGY AND AGRICULTURE 151 



THE HABITAT OF NATURALIZED COMMON 

 BAEBEEBY IX ILLINOIS 



Leo E. Tehox, State Natur-vl History Suryey 



An important problem in the prosecution of tlie coun- 

 try surYey for common barberry in Illinois, as weU as in 

 twelYe other states, has been to determine in what places 

 one might expect to find barberry shrubs escaped from 

 cultiYation. That some index of locations faYorable for 

 the naturalization of the shnib would greatly expedite 

 the sui'Yey can not be doubted. 



The presence of the common barberry, (^erfeens vul- 

 garis Linn.) in the United States, it is generally admitted, 

 is due to its introduction from Europe. DeCaudolle (1) 

 points to its absence from the islands west of America 

 and east of Asia, which might be supposed to serYe as dis- 

 tributional bridges between the two continents, as a geo- 

 graphical indication of the agency of man in its intro- 



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Map 1. Stephenson County. Scale ^4" = 1 mile. * Location of escaped plant- 

 ings. • Location of cultivated plantings. Figures indicate numbers of 

 bushes. 



