412 



WEED FLORA OF IOWA 



Fig. 243. B. Sandbur (Ccnchrus tnbuloides) . a. bur enlarged; b, spine; c and 



d, spikelet ; e, seed. 

 (After Hillman ; A, Bull. Nevada Agr. Exp. Sta., B, Bull. Michigan Agr. Exp. 



Sta.) 



Sandbur (Cenchrus tribuloides L.). 



Burs Avith sharp, straight, pubescent prickles; each bur with 

 6-20 globose spikelets. 



Green Foxtail {Set aria viridis (L.) Beauv.). 



"Seeds" about one-twelfth in. in length, biconvex, color light 

 green, or greenish; with flowering glume rounded, slightly granu- 



Figure 244A 



/9 yr~ ^e 



Figure 244 B 



Figure 244C 



Fig. 244. A. Green Foxtail (Setaria viridis). A and B, views of the floret; 

 A, the back of the glume ; B, showing the palea, its shining edges partially 

 covered by the edges of the glume. C, a floret covered by the empty 

 glumes (a spikelet), the figure showing the first and third glumes. D, a 

 group showing the natural size. 



B. Slightly enlarged spikelet. 



C. Whorled Millet (Setaria verticillata) . 



(A, after Hillman, Bull. Nevada Agr. Exp. Sta. ; B and C, drawings by Char- 

 lotte M. King.) 



