WHORLED ROSIN WEED 



a few broad, green bracts imbricated in three or more 

 rows, the innermost row membranous. Akenes are 

 flat, winged, and two-toothed at the top. Only those 

 of the ray-florets produce fertile seeds. 



Silphium appears In the wayside tangles of 

 northern Ohio in company with the Milkweeds, 

 Sweet Clover, Catnip, and Wild Carrot, and be- 

 gins to flower in August, continuing throughout 

 September. Its tall stems are well clothed with 

 long, stiff, dark green leaves, sometimes al- 

 ternate, oftener in whorls of three or four. 



The flower-heads are borne on branching 

 stems which apparently start from the summit 

 of the plant stem, making a whorled or corym- 

 bose inflorescence. In the very centre of this 

 whorl of stems rises one, short, erect, unbranched, 

 bearing a single flower-head, the first bloom and 

 often the largest of the flock. 



The plant has the height and poise of the 

 Sunflowers, though the rays are narrow and the 

 involucre quite different. Only the akenes of 

 the ray-florets are fertile, the disk-florets mas- 

 querade with both stamens and pistils, but pro- 



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