342 IOWA ACADEMY OF SCIENCE 



then reddish, or purplish. S., broadly ovate or nearly circular; 

 more pointed than A. graecizans; notch on one side of the nar- 

 rower end; thickest in the middle, curving- convexly to a rather 

 acute angle. 0., not important ; introduced from Tropical 

 America. 



26. Amaranthus graecizans L. Tumble-weed. L. .6 — 1. mm. 

 W. .4 — l.mm. Thickness about .3 mm. C, shining jet black. 

 S., nearly circular, thick at the middle and tapering to a rather 

 acute angle at the edge ; a notch on one side and fine reticula- 

 tions on the surface. 0., common in farm seeds, especially 

 clover. Introduced from Tropical America. 



27. Spergula arvensis L. Spurry. Corn Spurry. L. 1.2 — 1.8 

 mm. W. 1.2 — 1.6 mm. C, black with a narrow yellowish Wing 

 and a few short yellowish spines. S., broadly lens shaped with a 

 slight notch on one side, often with two notches close together 

 at the hilum ; surface with very minute shallow pits. 0., found 

 in grain fields and light sandy soil. Naturalized from Europe. 



28. Arenaria serpyllifolia L. Thyme-leaved Sandwort. L. 

 .3 — .5 mm. W. .2 — .4 mm. Thickness .2 — .3 mm. C, grayish 

 black or reddish brown, somewhat lead-colored. S., almost cir- 

 cular with the exception of a notch at one side ; surface covered 

 with about seven concentric or eccentric rows of oval-shaped 

 elevations on each side. 0., common in sand soil and found in 

 many farm seeds. Introduced from Europe. 



29. Stellaria media L. Cyrill. Common Chickweed. L. .8 

 — 1.2 mm. W. .6 — .9 mm. C, reddish yellow to brown. S., 

 disc-shaped, round, almost as thick at the edges as at the center; 

 surface covered with concentric rows of tubercle-like projec- 

 tions; a slight notch at one side at the scar. 0., very common 

 especially in imported and domestic clover seeds. Naturalized 

 from Europe. 



30. Cerastium viscosum L. Mouse-ear Chickweed. L. .6 — 

 .8 mm. W. .4 — .6 mm. C, reddish yellow-brown with less red 

 than in Stellaria media. S., somewhat circular or disc-shaped 

 but quite angled, somewhat wedge-shaped ; surface covered with 

 concentric rows of tubercle-like projections more pronounced 

 than in Stellaria media. 0., common in small clover and grass 

 seeds, "particularly in alsike and timothy from Canada" (Hill- 

 man). Introduced from Europe. 



