DESCRIPTIVE MANUAL 



89 



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

 only sterile plants, or flowering rather late in the season ; 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 muhlenbergii) . 

 (Photographed by W. Newell.) 



