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-Scribner, U. S. Dept. Agr.) 



purpurascens) , black-eyed Susan (EudbecMa hirta), Scribner's 

 panic (Panicum scribnerianum) , Philadelphia lily (Lilium phila- 

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

 closed gentian (Gentiana andrewsii), goldenrods (Solidago mis- 

 souriensis and S. rigida), aster (Aster laevis, 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 palmata), side oats (Bouteloua curtipendida) , 

 needle-grass (Stipa spartea), perennial ragweed (Ambrosia psilo- 

 stachya), sunflower (Helianthus occidentalis) , white aster (Aster 

 44 



