A SEED KEY TO COMMON WEEDS 377 



4. Angles acute, base contracted to a sharp point 



Eupatorium perfoliatum L. 82 



4. Angles slightly rounded, apex slightly rounded, base 



not contracted to a sharp point. .Rudbeckia hirta L. 91 

 4. Angles rounded, seed like a four sided pyramid with 

 short white hairs, not over 1.6 mm. long (fig. IX) 



Galinsoga parviflora Cav. 95 



3. Not pronouncedly square in cross section. 



4. Fluted cylindrical in shape, usually over 1.8 mm. 



long Hieracium sp. 117-118 



5. Quite attenuate at base. .Hieracium scabrum Michx. 118 



5. Abruptly contracted at base 



Hieracium aurantiacum L. 117 



4. Not fluted cylindrical in shape. 

 5. Over 1.1 mm. long. 



6. Pyramid or cone-shaped with numerous short 

 white hairs, pappus of chaffy bristles when 



present (fig. IX) Galinsoga parviflora Cav. 95 



6. Irregularly angled, surface not covered with hairs, 



no pappus, not reticulate, granular 



Plantago Rugelii Dene 78 



5. Under 1.1 mm. long. .Glyceria nervata (Willd.) Trin. 10 

 1. Not black or nearly so. 

 2. Nearly triangular in cross section. 



3. With more than 3 prominent longitudinal striations 



(fig. XXX) Daucus Carota L. 61 



3. With but 3 prominent longitudinal striations. 

 4. Rich dark reddish, comparatively short. 



5. Surface shining, angles distinct, sides nearly equal 



Rumex obtusifolius L. 14 



5. Surface dull, angles sometimes rounded, especially 



toward base Polygonum aviculare L. 16 



4. Light brown, comparatively long, a shallow groove on 



one side, angles often hairy Poa pratensis L. 9 



2. Not triangular in cross section. 

 3. Appearing white or light gray. 



4. Thin and wafer-like, white with darker markings. . 



Achillea Millefolium L. 96 



4. Background dark with 10 heavy white longitudinal 



ridges, not wafer-like (fig. XXVIII) 



Chrysanthemum Lcucanthemum L. 99 



3. Not appearing white or light gray. 

 4. Thin, wafer-like, cream-colored. 



5. With a slight margin around the edge, translucent, 

 "usually under .9 mm. long" B., sometimes slightly 



over 1 mm Erigeron annuus (L.) Pers. 83 



5. Without noticeable margin with noticeable hairs, 



"usually over .9 mm. long." Beal 



Erigeron canadensis L. 84 



