DESCRIPTIONS OF SOME COMMON WEEDS 



247 



some weed along roadsides and in pastures, being most 

 abundant in forest clearings ; it has been naturalized from 

 Europe. The seeds germinate in the spring, producing 

 a mass of leaves; the second season, a flowering stem 

 shoots rapidly up, producing flowers and seeds, then dies. 



Woolly Thistle (Cir- 

 sium canescens, Nutt.). 

 A branching perennial 

 two to four feet tall, 

 woolly throughout, the 

 branches bearing single 

 medium sized heads ; 

 stem angled, white wool- 

 ly ; radical leaves, eight 

 to twelve inches long, 

 prominently ribbed, end- 

 ing in stout spines, the 

 divisions usually two- 

 lobed ; stem leaves, ex- 

 cept the lower, one to 

 four inches long, pinnati- 

 fid, the upper sessile, 



slightly roughened and Fig I5? Burdock (Arctium 

 covered with a slight Common in the North across the con- 

 cottony down, the lower, tinent - (Clark-Hayden.) 

 white woolly ; heads 



one and one-half to two inches high, bracts of the invo- 

 lucre somewhat arachnoid, lower scales with a broad 

 base, glutinous ridge, and ending in a minutely toothed 

 spine, inner scales long attenuated, tips straw colored; 

 flowers purple. Minnesota and western Iowa to the west 

 and southwest. 



Prairie Thistle (Cirsium discolor, (Muhl.) Spreng.). 

 A tall, branching, leafy biennial, five to seven feet high, 

 with heads larger than those on the Canada thistle ; stem 

 grooved, slightly hirsute; radical leaves twelve to four- 



