4SS 



WEED FLORA OF IOWA 



Fig. 362A Pig. 362B 



Fig. 362. Seeds of Sunflowers. A. Prairie Sunflower (Helianthus petiolaris). 



B. Wood Sunflower (Helianthus strumosus) . 



(Drawings by L. Tt. Collins.) 



Wild Sunflower (Helianthus strumosus L.). 



Achenes obovate, flattened, several fine lines and a longitudinal 

 ridge on each side, one-sixth to one-fifth in. long, nearly glabrous: 

 yellowish or light brown, finely mottled, except near apex and base 

 which are lighter in color; lower end marked by small distinct 

 scar, occurring in a notch; upper end bearing large circular scar; 

 cotyledons 2, large, fleshy. 



Fig. 363A 



Fig. 363B Fig. 3630 Fig. 363D 



Pig. 363. Achenial hairs of Sunflower seeds. A. Artichoke (Helianthus tuber- 

 osus). B. Prairie Sunflower (Helianthus occidentalis) . C. Common Sun- 

 flower (Helianthus annuus). D. Prairie Sunflower (Helianthus petiolaris). 

 (Drawings by S. B. Fracker.) 



