674 WEED FLORA OP IOWA 



PEBCENTAGE CONTENTS OF DKT MATTER. 



Sow thistle {Bonchus oler- 



aceus) 



Cornflower {Centaurea cy- 



' anus) 



Spurrey (.Bpergula arverir. 



sis) 



Wild Radish (Raphanus 



raphanistrum) 



Persicaria or red-shank 



(Polygonum persicaria) . ' 

 Yarrojtf (Achillea millefol- 



ium) 



Average of .six weeds 



2.39 



2.30 



2.36 



1.85 



3.12 



2.30 

 2.38 



14.95 

 8.12 



10.12 

 5.22 



10.58 



9.61 

 9.76 



4. WEEDS PULL DOWN THE CROPS. 



' "Weeds like morning-glory, bindweed, wild buckwheat, and others, 

 pull down a cultivated plant and then prevent the formation of a 

 good. crop. 



5. WEEDS ARE INJURIOUS BECAUSE IT IS DIFFICULT TO RE- 

 MOVE THE SEEDS. 



It is difficult in many eases to remove weed seeds from seed of 

 various kinds. Buckhorn can be removed with difficulty from 

 clover seed ; peppergrass with difficulty from timothy seed ; greater 

 ragweed from wheat ; wild oats from oats ; quack grass from brome 

 grass; cockle from wheat. These impurities often greatly reduce 

 the quality of the grain or seed. 



6. WEEDS HARBOR INSECTS. 

 Long gives the following insects found on weeds: 



