Flowers purple; achenes dull brown, often spotted with black, straight or curved, slightly flattened, oblong-prismatic with 3-5 narrowly ridged angles, and occasionally other smaller ridges, 4.5-6 mm. long. Introduced from Europe.
=Biennial Wormwood.= _Artemisia biennis_ Willd. Achenes dark brown, smooth, somewhat flattened, 3-4 angled, obovate, narrowed at the base .8-1.3 mm. long. Native in the northwestern United States and introduced east with grass seeds. Moist land.
=Smaller Bur-Marigold.= _Bidens cernua_ L. Flowers yellow; achenes 4-6 mm. long, dull brown, the awns lighter, flattened, 4-angled, wedge-shaped, awns 2-4, barbed downward as also are the ribs. Native of this country. Low lands.
=Purple-stemmed Swamp Beggar-ticks.= _Bidens connata_ Muhl. Flowers orange; achenes brown, wedge-shaped or obovate, hairy, tubercled, flattened, 4-angled, 4-toothed, 4-6 mm. long, achenes and teeth downwardly barbed. Swamps, common.
=Beggar-ticks.= _Bidens frondosa_ L. Achenes dull brown, tubercled, much flattened, obovate or oval, 6-12 mm. long, awns usually 2, spreading barbed downward. Low lands.
=Star Thistle.= _Centaurea solstitialis_ L. Achene cream white to mottled brown, flattened, oval about 2 mm. long; scar of attachment in a notch of one edge above the rounded base, apex truncate with a small tubercle in the middle. Found in seeds of alfalfa. A ragged plant from Europe.
=Ox-eye Daisy.= _Chrysanthemum Leucanthemum_ L. Flowers white; achenes brown or black with ten white conspicuous vertical ribs, narrowly obovate 1.5-1.8 mm. long, bearing a tubercle at the apex. Introduced from Europe. Becoming common. A prominent weed in old pastures and meadows.
=Chickory.= _Chichorium Intybus_ L. Flowers yellow; achenes light brown, more or less mottled or spotted with black, straight or curved, 4-5 angled, flattened, apex truncate crowned with a double row of minute scales. Achenes 2.5-3 mm. long. Introduced from Europe.
=Canada Thistle.= _Cirsium arvense_ (L.) Scop. _Carduus arvensis_ (L.) Robs. Flowers purple or white; achenes smooth, light brown, curved or straight, narrowly obovoid or oblong, slightly flattened, 2-3 mm. long, apex truncate, cup-shaped with a tubercle in the center. Introduced from Europe. A weed of first rank.