attened; seeds reddish brown, circular, broad oval, or rhombic in
outline, about 1.5 mm. in diameter, flat on one side showing a slight
groove, the other side convex, irregular owing to pressure in the pod.
Cotyledons accumbent. Introduced from Europe. A thrifty weed of the
mustard family.

[Illustration: Fig. 81.]

=Charlock.= _Brassica arvensis_ (L.) B. S. P. Pods tipped with a
flattened elongated-conic, often 1-seeded beak. See also cuts of
rutabaga and black mustard. Introduced from Europe. See statements last
above.

[Illustration: Fig. 82.]

=Rutabaga.= _Brassica campestris_ L. Seed dull, light or dark reddish
brown, roughened by an indistinct net work of ridges, very nearly
spherical, 1.4-1.8 mm. in diameter. Much cultivated, inclined to escape.
Included here for comparison with other species. Introduced from Europe.

[Illustration: Fig. 83.]

=Indian Mustard.= _Brassica juncea_ (L.) Cossos. See also cuts of turnip
and black mustard. Introduced from Europe.

[Illustration: Fig. 84.]

=Black Mustard.= _Brassica nigra_ (L.) Koch. Seeds dark brown to reddish
brown, 1-1.7 mm., spherical, or broadly oblong, not flattened. The
surface of well developed specimens presents a delicate but evident net
work of fine ridges which appear under the lens as dark lines. The scar
(hilum) is a whitish, elevated spot, at one extremity of the oblong
seeds. See cuts of seeds of turnip. Introduced from Europe. A vigorous
persistent weed.

[Illustration: Fig. 85.]

=Small Fruited False-Flax.= _Camelina microcarpa_ Andrz. Flowers small,
yellow; pods pear-shaped, flattened, about 6 mm. long, surrounded by a
vertical ridge; seeds reddish brown, granular, usually broad-oval, about
1 mm. long, slightly flattened, the vertical ridge much less prominent
than in C. sativa. When wet the seed is soon covered with mucilage. Not
yet very common. Naturalized from Europe.

[Illustration: Fig. 86.]

=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 Burs