DESCRIPTIONS OF SOME COMMON WEEDS 143 



Wide!} r distributed all over northern United States, and 

 a pernicious weed in cultivated fields. 



Bristly Foxtail (Setaria verticillata, (L.) Beauv.). A 

 low, spreading, much-branched annual from one to two 

 and one-half feet high ; lanceolate leaves, two to seven 

 inches long, somewhat narrower than those of 5\ viridis, 

 and from one-fourth to one-half inch wide ; sheaths 

 smooth, rough on the margins and veins ; spike cylindri- 

 cal from one to five inches long, composed of short, cylin- 

 drical clusters, with short bristles, a little longer than the 

 spike, either single or in pairs and barbed downward; 

 seeds small, greenish, minutely cross-striated and 

 wrinkled ; blooming time from June to September. Quite 

 abundant in the East, and west to Nebraska; unless 

 strong measures are taken to eradicate "it, it will soon be- 

 come as troublesome as the other species. Because of its 

 downwardly barbed bristles, it is easily disseminated by 

 animals. 



Green Foxtail (Setaria viridis, (L.) Beauv.). A 

 smooth, erect annual, from one to three feet high, with 

 leaves long, rough margined, greenish, more or less com- 

 pound, cylindrical spikes from one to six inches long, 

 with few bristles; spikelets shorter than the bristles, 

 about one-half inch long, the chaff of the second and 

 third glumes equaling the minute chaff of the fourth 

 glume, which is faintly transversely wrinkled below or 

 only striate and pitted; blooms 'from July to September. 

 A single head of the green foxtail produces an enormous 

 number of seeds, which appear to have considerable vital- 

 ity, hence when the plant once becomes established in a 

 field, it is very difficult to remove it. This difficulty is in- 

 creased by the habit of the grass of forming tufts. The 

 species common in the northern states and a trouble- 

 some weed in corn fields. 



Sandbur (Ccnchrus tribuloides, L.). An erect annual 

 one to four feet high, with spreading, or ascending, much- 



