250 IOWA ACADEMY OF SCIENCES. 



572. B. cenuKi L. Smaller Bur-Marigold. Veiy com- 



. mon ill iiuirslies or other wet places; the heads 

 nodding in fruit. 



573. B. frondom L. Spanish Needles. Common; a 



troublesome weed in low fields. 

 Helenium L. 



574. H. autionnale L. Sneezeweed. Common on low 



prairies. 

 Achillea L. 



575. A. ii/i/lcfoluiui L. Yarrow. Milfoil. A common 



and troublesome weed, introduced in grass 



seed, native to North America as well as Europe 



and Asia. 

 Anthemis L. Mayweed. 



57(). A. cofu/ah. {Maruta cotula DC.) Frequent around 



old dwellings. 

 Artemisia L. Wormwood. 



577. A. caudata Michx. Frequent on dry knolls. 



578. A. dracunculoides Pursh. Woods and prairies; fre- 



quent. 



579. A. ahsiiifhiu]}! L. Introduced into waste places 



from Europe. 



580. A. biennis Willd. Very common, especially as a 



weed in wet fields. 



581. A. gnaphalodes Nutt. {A. ludoviciana Nutt. var. 



gnaphalodes Torr. & Gray.) Woods and prairies; 

 very common. 



Erechtites Kaf. 



582. E. hieraci folia (L.) Raf. Fire-weed. Rare in cul- 



tivated ground; probably introduced into our 

 county. 

 Mesadenia Raf. 



583. il/. tuheroHa' i'^nit.) Britton. {Cacalia tnherosa 



Nutt.) Common on prairies. 

 Senecio L. 



584. S. (iKrcK.s L. Grolden Ragwort. Squaw-weed. 



Frequent on prairies, usually growing in 

 patches. 



