=False Flax.= _Camelina saliva_ (L.) Crantz. The common name is derived from the fact that it is a weed of flax fields in Europe. Flowers small, yellowish; pods pear-shaped, slightly flattened, 8-10 mm. long, surrounded by a vertical ridge. Seeds reddish yellow, granular, usually oval, 2-3 mm. long, one side flat or roundish, the other furnished with a prominent vertical or oblique ridge. Seed incumbent. When wet the seed is soon covered with mucilage. Naturalized from Europe. [Illustration: Fig. 87.] =Shepherd's Purse.= _Capsella Bursa-pastoris_ (L.) Medic. _Bursa Bursa-pastoris_ (L.) Britton. Flowers small, white; pods flat, nearly triangular, about 4 mm. long. Seeds reddish yellow, granular, oblong, slightly flattened, 1 mm. or less long. Each side usually bearing two longitudinal grooves, separating the surface into three nearly equal parts, these grooves indicating the position of the parts of the embryo. When placed in water, a copious coat of transparent mucilage appears on the surface. In Nevada and Colorado a great pest in fields of Alfalfa. [Illustration: Fig. 88.] =Hare's Ear.= _Conringia orientalis_ (L.) Dumort. Seeds brown, surface checked off into minute irregular pits or patches; broad oval, 2-2.5 mm. long, in section nearly circular, except two opposite slight grooves near one side. Cotyledons incumbent. Introduced, not common. [Illustration: Fig. 89.] =Sand Rocket.= _Diplotaxis muralis_ (L.) DC. Flowers yellow, seeds reddish yellow or reddish brown, broad oval, somewhat flattened. Mucilaginous when wet. Introduced from Europe. A vigorous weed. [Illustration: Fig. 90.] =Worm-seed or Treacle Mustard.= _Erysimum cheiranthoides_ L. Flowers yellow; seeds reddish yellow, smooth, dull, about 1.2 mm. long, ovoid or oval, more or less flattened, varying much in shape; some of them acute, rhombic or triangular, becoming mucilaginous when wet. Probably introduced from Europe. If not already in some portions of the state, we may at any time expect to find three other species of Erysimum. A vigorous and prominent weed. [Illustration: Fig. 91.] =Apetalous Pepper-Grass.= _Lepidium apetalum_ Willd. Petals usually wanting, sometimes 2 and minute; pods flat, nearly circular; seeds reddish yellow, flattened, ovate, 1.5-1.8 mm. long, or more exactly, nearly straight on one side and roundish on the other. Mucilaginous when wet. Cotyledons incumbent. When well developed in open places it becomes a tumble weed. Apparently naturalized from Europe. [Illustration: Fig. 92.] =Field Pepper-Grass or Cow Cress.= _Lepidium campestre_ (L.) R. Br. Petals white; pods flat, nearly circular; seeds dull, dark brown, obovoid, with base acute, more or less flattened on three sides, 2-2.5 mm. long. Mucilaginous when wet. Cotyledons incumbent. Naturalized from Europe. [Illustration: Fig. 93.]