Sonchus arvensis L Field sowthistle. 



Near greenhouses, location 18. 

 Sonchus cleraceus L Common sowthistle. 



Common in cultivated ground. 



Taraxacum erythrospermum Andrz. (T. laevigatum 



of many authors) Smooth dandelion. 



Common everywhere. 



Taraxacum officinale Weber {Leontodon taraxacum L.) 



Common dandelion. 

 Common. 



Verbesina occidentalis (L.) Walt. Crownbeard. 



Meadows and thickets. 

 Vernonia glauca (L.) Willd Ironweed. 



Margin of woods and in fields. 

 Vernonia noveboracensis (L.) Michx. 



Woods and meadows. 



Xanthium italicum Moretti (X. saccharatum sensu Widder, X. commune of 

 the 1919 "Flora of the District of Columbia," in part) . . .Cockle-bur. 



Cultivated ground and waste places. 



47 



