482 



WEED FLORA OF IOWA 



Daisy Fleabane {Erigeron a/rmuus (D.) Pers.)- 

 Achenes pale straw color, smooth, shining, flattened, oboTate; 

 length 0.7-0.9 mm.; the apex bears a row of small straw-<jolored 

 bristles. 



Horseweed {Erigeron ccmadensis L.). 



Achenes one-twenty-fourth to one-twentieth in. long, white or 

 whitish, oblong lance-shaped, much flattened, one side often more 

 convex than the other; scar of seed witli small, whitish, raised 



Fig. 355D 



Aster laevis. B. Aster 

 macrophyllus. . C. Aster drummondii. T>. Bigelovia nudata. 

 (Drawings by Mary A. Nichols and S. B. Fracker.) 



Fig. 355A Fig 355B , Fig. 3550 



Fig. 355. Achenial hairs of Asters and Bigelovia. A. 



border, pubescent; pappus small, of numerous, fragile, capillary 

 bristles, usually breaking away. With grass seeds and lawn mix- 

 tures. 



Cup Plant {SUphium perfoUatwm L.). 



Achenes large, two-fifths in. in length, dorsally flattened, 2- 

 winged, notched at apex, grayish or bronze-colored, margins thin. 



Marsh Elder {Iva xanthifolia Nutt.). 



Achenes obovoid, brown to black, with somewhat flattened longi- 

 tudinal faces 1.5 to 2 mm. in length, longitudinally striate with 

 fine markings. 



Small Ragweed {Ambrosia wrtendsiaefolia L.). 



Involucre containing a single achene one-twelfth to one-sixth in. 

 long, obovoid or globular, tipped by a tapering beak one-quarter 

 length of involucre; ridges several (4-10), prominent, with pro- 

 jecting tubercles, short, acute ; color grayish or brownish, pubescent ; 



