WEED MIGRATION 



689 



Fig. 532. Blue Stem (.Andropogon scoparius). A plant common to the 

 prairies of Iowa, a, spikelet ; b, c, first and second glumes ; d, third 

 glume ; f, lodicules stamens and pistil. 



(Lamson-Sorlbner, U. S. Dept. Agr.) 



purpurascens) , hlack-eyed. Susan {Budbechm hirta), Scribner's 

 panic (Panicum scribnerianum) , Philadelphia lily {Liliium phila- 

 delphicum) , lobelia {Lobelia spicata), sorrel {Oxalis violacea), 

 closed gentian {Gentiana andrewsii), goldenrods {SoUdago mis- 

 souriensis and 8. rigi^a), aster {Aster laems, A. azureus) and a 

 host of other associates. Compare with this an area in the Wis- 

 consin drift where such plants as blue vervain {Verbena stricta), 

 coreopsis {Coreopsis palmafa), side oats {BoiUeloua curtipendula) , 

 needle-grass {Stipa spartea), perennial ragweed {Ambrosia psilo-. 

 stachya), sunflower {Selianihus ocddentaUs), white aster {Aster 

 44 



