468 



WEED FLORA OF IOWA 



^ 



Figure 334A 



Figure 334B 



Fig. 334. A, Corn Gromwell (.Lithospermum arvense). A, difterent views of 

 nutlets, B, one bearing the flower-receptacle and portion of the stem, C, 

 the natural size of the larger nutlets. 



B, Viper's Bugloss {Echmm vulgare). 



(A, after Hillman, Bull. Mich. Agr. Exp. Sta. ; B, dra-«vn by L. R. Collins.) 



Viper's Bugloss {Echmm vulgare L.). 



Nutlets ereet, ovoid, one-eleventh in. in length, back distinctly 

 convex ; seed straight or curved ; outer f ac& with distinct ridge ; 

 surface rugose ; color white, base flattened. 



VERBENACEAB, VERVAIN FAMILY. 



Large-bracted Vervain {yerbena bracteosa Mx.). 



Nutlets cylindrical, 3-sided, outer face convex, one-tenth in. in 

 length, outer face rugose at upper end, lower end marked by lines, 

 inner face pitted, scar somewhat elevated, whitish. In seeds of 

 clovers and grasses. 



Da b 



; Figure 336A Figure 335B 



Fio. 335. A. Large-bracted Vervain (.Verbena bracteosa). B. Blue Vervain 

 (.Verbena hastata). A, the outer face, and B, the inner face of a nutlet; the 

 latter shows the whitish, spongy scar at the base. C, a group showing the 

 natural size. D, a section of a nutlet, taken lengthwise. 

 (A, drawing by C. M. King; B, after Hillman, Bull. Nev. Agr. Exp. Sta.) 



