A SEED KEY TO COMMON WEEDS 341 



black. S., triangular in cross section tapering at both ends 

 to a somewhat attenuate point ; faces somewhat concave. O., 

 common in all kinds of farm seeds from all sources, particular- 

 ly in the seeds of cereals, millet and flax. Introduced from 

 Europe. 



20. Polygonum, scamdens. L. Climbing False Buckwheat. 

 L. 3.5 — 7.2 mm. W. 3. — 4.8 mm. C, shining jet black. S., tri- 

 angular in cross section, tapering almost equally at each 

 end to a point; faces slightly concave; angles slightly rounded. 

 0., not common. Introduced from Japan. 



21. Chenopodium kybridum L. Maple -leaved Goosefoot. 

 L. 1.2—2.2 mm. W. 1.2—2.2 mm. Thickness .4— .6 mm. C, 

 shining black or gray. S., almost round with a shallow notch 

 on one side ; sides equally convex ; a groove on one side lead- 

 ing from the notch to near the center. 0., not very common, 

 but often found on waste land. Native. 



22. Chenopodium album L. Lamb's Quarters, Pigweed. L. 

 1. — 1.5 mm. W. .8 — 1.5 mm. C, dull black or shining or 

 gray. S., circular except for a notch on one side ; one face 

 nearly flat, the other convex ; the edge rounded. 0., common 

 in all kinds of farm seeds particularly clover and grass seeds. 

 Introduced from Europe. 



23. Atriplex patula L. Spreading Orache. L. 1.3 — 1.9 mm. 

 W. 1.4 — 1.7 mm. C, black or dull dark gray speckled with 

 light gray when the involucre is on ; shining black with the 

 involucre off. S., nearly circular with a slight notch on one 

 side ; face nearly flat ; groove on one side running from the 

 scar towards but not to the center. 0., not common. Intro- 

 duced from Europe. 



24. Amarantlnts retroflexus L. Rough Pigweed. L. .8 — 1.2 

 mm. W. .6 — .9 mm. C, shining jet black or reddish if im- 

 mature. S., obovate or broadly oval with a slight notch at 

 one side of the narrower end ; smooth surface very finely re- 

 ticulated with fine lines when seen with a low-power micro- 

 scope. "When seen edgewise the hem-like margin in this 

 seed is less prominent than in A. graecizans, A. hybridus and 

 A. blitoides." Beal. 0., common in various kinds of farm 

 seeds, especially clover and timothy. 



25. Anmranthus hybridus h. Slender Pigweed. L. 1. — 1.5 

 mm. W. .8 — 1.4 mm. C, shining black unless immature and 



