WEEDS OP IOWA, MINNESOTA AND WISCONSIN 
59 
The striking differences occur in a few of the common weeds 
of central Iowa and northern Minnesota. The boreal weeds like 
the European Crowfoot (Ranuncukis acris), fireweed {Epiloh- 
ium angustifolmm) , the Canada thistle {Cirsium arvense), Lo- 
phanthus anisatens become increasingly common in the north. 
The absence of the Rammculus acris, fireweed, and Lophanthus 
in our flora is of interest. The abundance of corn cockle and 
tumbling mustard vetch {Vida sativa) in the north can be ac- 
counted for easily because of the shipment of grain from west- 
ern Minnesota and Dakota. 
Botanical Laboratory. 
Iowa State College. 
