450 THE SMALL GRAINS 



Storm King type, the last having the side panicle. Hill- 

 man has found' what are apparently similar false wild 

 oats in the cultivated varieties of Colorado. 

 , 489. Pigeon weed or wheat-thief (Lithospermum 

 arvense, Linn.) is a winter annual common in the eastern 

 states and western Ontario, and troublesome in fields of 

 winter wheat. It is wide branching, white flowered, and 

 produces many early-ripening seeds. The seeds are 

 | inch long, and deeply and irregularly grooved, with 

 prominent ridges between the grooves. They are recog- 

 nized by the oval or obtusely 3- to 5-angled basal scar 

 (Fig. 141 g). 



The seeds are common in poorly cleaned winter wheat 

 and rye, and are occasionally found in clover seed. The 

 weed may be eradicated by a rotation including an inter- 

 tilled crop and spring sown grain. Late fall or spring 

 plowing will kill plants that start in the autumn. 



490. Sunflower (Helianthiis annuus, Linn.). Sev- 

 eral species of sunflower are found in grain fields, but 

 this one is most general in its distribution. In large parts 

 of the Great Plains it is the worst cereal weed pest. Its 

 worst effect is in usurping space belonging to the grow- 

 ing crop and filling the sheaves at harvest time, wasting 

 labor and time and obstructing the curing of the grain. 

 Some seeds get into thrashed grain but usually the weed 

 does not mature as soon as the crop. 



The stems of the sunflower are stout, sparingly branched, 

 rough or hairy, leaves thick, ridged, and rough; heads 

 very large, nearly solitary, with bright yellow ray flowers, 

 and black disks ; seeds J inch long, narrowly oblong, egg- 

 shaped in outline, flattened and angular or grooved length- 

 wise. The seeds are sometimes abundant in the screen- 

 ings of western grain (Fig. 141 i). 



