DESCRIPTIVE MANUAL 89 



bright rose color; stamcBs 5, styles 2-cleft, exerted. Frequently 

 only sterile plants, or flowering rather late in the season j trichomes 

 multicellular, at base with thick outer epidermal walls. 



Distribution. — Common from Canada to Florida and west, found 

 in all parts of Iowa ; an exceedingly variable plant ; sometimes found 

 in very moist situations, and in stagnant water, or in somewhat 

 higher but poorly drained situations. The black, thickish roots are 

 quite characteristic of the plant. 



Extermination. — ^Marsh smartweed or tanweed, as it is sometimes 

 called, is a persistent perennial and since the weed grows in wet 

 places it is particularly difficult to destroy. The best method of 



Fig. 51. Tanweed, Marsh Smartweed (Polygonum muhlenbergU). 

 (Photographed by W. Newell.) 



