486 



WEED FLORA OF IOWA 



twelfth in. long; color dull; smooth or covered with yellowish 

 hairs ; achenes 2 in each bur. 



Cocklebur (Xanthium strumarium L.). 



Involucre one in. long; brownish in color; prominently bristly 

 spines curved; achenes 2 in each bur; closely resembles X\ can- 

 adense. 



Rough-Ox-eye (Heliopsis scdbra Dunal). 



Achenes thick, obtusely 3-4-angled, with truncate summit; one- 

 eighth to one-seventh in. long; margins pubescent; blackish; apex 

 somewhat depressed; scar at base light or straw-colored; pappus 

 none. 



Fig. 360B 



Fig. 360C 



Fig. 360A Fig. 360A1 



Fig. 360. Seeds of Heliopsis and Rudbeckia. A, Al, Ox-eye (.Heliopsis scabra). 

 B. Black-eyed Susan or Nigger-head (Rudbeckia hirta) ; a, two views of 

 achenes, b, achenes, natural size. C. Coneflower (Rudbeckia laciniata). 



(A, C, drawings by L. Collins; Al, Charlotte M. King; B, after Hillman, Bull. 

 Mich. Agr. Exp. Sta.) 



Nigger-head (Rudbeckia hirta L.). 



Achene purplish black, 1.5-1.8 mm. long, tapering slightly from 

 base to apex ; a distinct ridge at each of the 4 angles of the achene ; 

 each side with fine longitudinal strips; no pappus. 



Cone-flower (Rudbeckia laciniata L.). 



Achenes 4-angled, brownish, truncate, one-fifth in. long; min- 

 utely roughened; upper end with projecting truncate point; apex 

 with an inconspicuous scar. 



Gray-headed Cone-flower (Lepachys pinnata Torr. & Gray). 



Achene short, flattened or angular, one-tenth of an inch long, 2 

 slightly marginal wings, and 2 intermediate ones, or only 1, convex ; 

 apex whitish, depressed with slight projecting scar; base with 



