452 



WEED FLORA OF IOWA 



€ 



Fig. 306. White Sweet Clover (Melilotus alba). A, a group of seeds. B, the 

 pods ; the central one without the calyx. C, the embryo. D, a group of 

 seeds and pods, natural size. 



(After Hillman, Bull. Nev. Agr. Exp. Sta.) 



Yellow Sweet Clover (Melilotus officinalis (L.) Lam.). 



Pods one-seventh in. in length; rugose, more evenly transversely 

 wrinkled than in M. alba; seeds suhspherical or elliptical to kidney- 





o 



Fig. 307. Yellow Sweet Clover (Melilotus officinalis) . A, seeds. B, pods; the 

 one at the right without the calyx, and showing the contracted base. C, a 

 view of a seed in cross section, showing cotyledons and caulicle. D, a group 

 of seeds and pods, natural size. 



(After Hillman, Bull. Nev. Agr. Exp. Sta.) 



shaped, one-twelfth to one-tenth in. in length, smooth ; yellowish or 

 brownish to greenish; with small micropilar processes. 



Bur Clover (Medicago hispida Gaertn.). 



Seeds kidney-shaped, occasionally sausage-shaped, both sides con- 

 vex, one-sixth in. in length, larger than alfalfa, variable in size ; 

 color lighter than in alfalfa seed; scar about middle of seed, close 

 to prominent micropilar processes ; pods large, spirally twisted into 

 several flat coils, covered by pointed projections; the prickles either 

 straight or curved ; each pod several-seeded ; seeds have general re- 

 semblance to alfalfa seed in form and color. 



