DESCRIPTIONS OF SOME COMMON WEEDS 243 



few scales at the base, one row united to form a cup ; 

 achenes slender, four-angled, pappus a row of chaffy scales 

 divided into numerous rough bristles ; many seeds. Com- 

 mon from western Iowa and Minnesota to Illinois and 

 the Southwest. In this section of the country it occupies 

 ground like that over-run with mayweed. 



Yarrow (Achillca mill e folium, L.). Perennial herb 

 from one to two feet high ; simple stems, leaves twice- 

 pinnately parted, consisting of crowded linear divisions ; 

 flowers in compound, flat-topped corymbs; heads many- 

 flowered, radiate; rays four to five, white; scales of the 

 involucre with scarious margins; receptacles chaffy; disk 

 flowers small, tubular; achenes oblong, flattened; pappus 

 none. Common from the Atlantic to the Pacific ; in the 

 East found in old fields and dry hills ; abundant in open 

 parks and rocky dry soils in the Rocky Mountains up to 

 the timber line ; native also to Europe where it is used as 

 an ornamental plant ; the form with rose-colored ray- 

 flowers is also cultivated. Sheep will eat the weed. 



Mayweed, Dog Fennel (Anthemis Cotula, L.). An 

 acrid, branching, strong-scented perennial from one to 

 two feet high with leaves thrice pinnately dissected ; 

 heads solitary and many-flowered, ray-flowers white, and 

 pistillate, fertile or neutral ; disk-flower yellow, small and 

 tubular; involucre consists of numerous small, imbri- 

 cated, dry and scarious scales ; achenes terete or ribbed, 

 smooth, truncate ; pappus none or merely a minute crown. 

 Common in Europe where it is native, but introduced 

 into the United States and very widely spread, being scat- 

 tered from the Atlantic to the Dakotas and Nebraska 

 throughout the northern states. Also found in Wash- 

 ington and Oregon. 



Corn Chamomile (Anthemis arvensis, L.). A pubes- 

 cent annual or biennial closely resembling mayweed, but 

 not so strongly scented ; sessile leaves, one to two-pin- 

 nately parted; numerous heads with oblong, obtuse 



