Fig 179. [Ragweed. Ambrosia artemisiifolia] L.

Ragweed. Ambrosia artemisiifolia L. Achenes hard, straw-colored to light brown or black, top-shaped, broadly oval, 2.5–3 mm. long, besides the beak 1.5 mm. long, the sides irregularly ridged vertically, with 5–10 short teeth at the apex. Sometimes the hard covering is removed by a clover huller, exposing the naked seed. Native of the U. S.

Fig 180. [Great Ragweed. Ambrosia trifida] L.

Great Ragweed. Ambrosia trifida L. Achenes hard, brown, more or less mottled, top-shaped, 7–8 mm. besides the stout beak 2–3 mm. long, sides with 5 stout ridges terminating in 5 short teeth. Native to the United States. River bottoms, low land, sometimes 15 ft. high.

Fig 181. [Corn Camomile. Anthemis arvensis] L.

Corn Camomile. Anthemis arvensis L. Achenes very variable, creamy white to light brown, oblong, wedge-shaped in outline, circular to four-angled in cross-section, more or less ribbed lengthwise, a ripple-shaped scar at the narrow end; apex truncate with a minute projection in the center, often with a narrow ridge about the margin. About 1.7 mm. long. Introduced from Europe. Seldom troublesome in Michigan.