When mature, large plants become tumble weeds. Apparently native to this country.
=Ball Mustard.= _Neslia paniculata_ (L.) Desv. Small fruits, greenish to light yellowish-brown, globular, 2 mm. in diameter, covered with net-veined ridges; 1-2 seeded, cotyledons incumbent. Not yet known in Michigan but may arrive any time. Native of Europe.
=Tall or Tumbling Mustard.= _Sisymbrium altissimum_ L. Flowers cream-color; pods long and narrow; seeds reddish yellow, oblong, about 1.5 mm. long, the apex winged. Mucilaginous when wet. Cotyledons incumbent. Introduced from Europe. One of the worst weeds in the northwest.
=Hedge Mustard.= _Sisymbrium officinale_ (L.) Scop. Flowers yellow, seeds reddish brown or yellow, oblong, while lying on the flat side, circular in outline at the middle as viewed from the edge, straight on one side from the middle tapering to each end. 1-1.5 mm. long. Mucilaginous when wet. Cotyledons incumbent. Introduced from Europe.
=Penny Cress.= _Thlaspi arvense_ L. Flowers white; pods thin, double convex, nearly circular; seeds deep reddish brown, flat-oval or ovate, covered on each side by 12-14 curved ridges which originate and terminate at the narrow extremity. 1.5-2 mm. long. Cotyledons accumbent. When eaten by cows the milk and meat has a disagreeable taste. A bad weed, especially in the north-west. Introduced from Europe.
=Mossy Stonecrop.= _Sedum acre_ L. Seed light, reddish-yellow, somewhat glossy, obovate to oblong, pointed at the base, slightly anatropous, compressed, 6-7 mm. long. This mossy little plant is persistent when once established in sandy soil. Introduced from Europe.
=Tall Hairy Agrimony.= _Agrimonia gryposepala_ Wahl. _Agrimonia hirsuta_ (Muhl.) Bicknell. Flowers yellow. Bur, consisting of calyx and two included fruits inside of which are two seeds; lower part of bur, top-shaped, rough, grooved, above which are numerous hooked prickles in several rows, the whole 7-10 mm. long. Native of woods in this country; seeds mottled brown, flat on one side, 2.5 by 2.5 mm. not found mixed with grass seed. Several other species are nearly as troublesome as this one. Seldom found out of the woods.
=Small-flowered Agrimony.= _Agrimonia parviflora_ Ait. Flowers yellow; fruit 5-6 mm. long and nearly as wide including the hooked bristles; bristles few, erect or spreading, scarcely any recurved; seeds light brown, broad oval, 2.7 by 2.5 mm. with a rounded point at the base more pronounced than in the former species. Shady places.