w colored, 0.8-1.2 mm. in diameter, oblong, 0.3 mm. thick, when
seen in cross sections, surface uneven with minute wrinkles, pits and
dots flattened, broad oval to circular, three-sided, bearing the remains
of a short curved style. Rich, low woods, not a common weed.

[Illustration: Fig. 74.]

=Bitter or Tall Buttercup.= _Ranunculus acris_ L. Achenes dull, dark
brown, two-beaked, somewhat lens-shaped, 3-4 mm. long, one edge very
slightly convex, the other prominently so, or somewhat semicircular in
outline, hem-like margin, obscure. Introduced from Europe. Low land.

[Illustration: Fig. 75.]

=Bulbous Buttercup.= _Ranunculus bulbosus_ L. Achenes dull brown, nearly
circular, diameter 3-4 mm.; beak short, turned to one side, surrounded
by a narrow, hem-like margin. In June, many meadows of New England and
New York are yellow with great numbers of flowers. Introduced from
Europe. Upland; fortunately not yet common in this state.

[Illustration: Fig. 76.]

=Creeping Buttercup.= _Ranunculus repens_ L. Achenes plump, dull,
light-brown, nearly circular, diameter 3-4 or more mm.; beak more or
less hooked, hem-like margin conspicuous. This species usually seeds
very sparingly, but when once introduced, it looses no time in spreading
by creeping stems. Introduced from Europe. Moist land; a rapid spreader
by runners.

POPPY FAMILY. PAPAVERACEAE.

[Illustration: Fig. 77.]

=Celandine.= _Chelidonium majus_ L. Yellow sap, yellow flowers; seeds
dark brown to almost black, ovoid, 1.2-1.5 mm. long, with 10-12 curved
vertical rows of small square depressions on each side; projecting from
one side a prominent white or cream-colored ridge, irregularly wrinkled
when dry. Introduced from Europe. Persistent.

MUSTARD FAMILY. CRUCIFERAE.

[Illustration: Fig. 78.]

=Yellow or Small Alyssum.= _Alyssum alyssoides_ L. Flowers yellow; fruit
nearly circular; seeds rich yellowish brown, about 1.5 mm. long, nearly
straight on one edge, flattened slightly, convex on each side or one
side flat, surrounded by a thin wing. Cotyledons accumbent. Introduced
from Europe.

[Illustration: Fig. 79.]

=Yellow Rocket. Winter Cress.= _Barbarea vulgaris_ R. Br. (_Barbarea
Barbarea_ L. Mac. M.) Seeds roughened, dull, light brown, irregularly
flattened, broad oval, circular-oval, circular-oblong, cotyledons
accumbent. Introduced from Europe.

[Illustration: Fig. 80.]

=Hoary Alyssum.= _Berteroa incana_ (L.) D. C. Flowers white; pods oval,
fl