wn, linear, with 5 broad, rounded ribs; achene 4-6.5 mm. long,
straight or curved, the outer traversed, with low transverse ridges.
Introduced from Europe.

[Illustration: Fig. 207.]

=Black-eyed Susan. Yellow Daisy.= _Rudbeckia hirta_ L. Achene
purple-brown to black, slightly tapering from base to apex 1.5-1.8 mm.
long, base abruptly pointed, apex truncate, in cross section nearly
square, having 5-7 slender vertical ridges on each side besides a larger
one at each of the four corners. Widely distributed in meadows and
pastures.

[Illustration: Fig. 208.]

=Corn Sow-Thistles.= _Sonchus arvensis_ L. Flowers yellow; achenes dull,
dark reddish brown, oblong, extremities blunt, slightly flattened,
bearing four coarse, fold-like ridges, with two smaller ridges between
each of the two large ones, transversely wrinkled, 2.5-3 mm. long. This
species is a perennial spreading by roots-stalks as well as by seeds.
Introduced in Europe.

[Illustration: Fig. 209.]

=Spiny Sow-Thistle.= _Sonchus asper_ (L.) Hill. Flowers pale yellow;
achenes dull straw-color to reddish brown, much flattened, obovate,
oblong, extremities blunt, each side bearing 3-5 vertical ridges,
surface nearly smooth, 2.5-3 mm. long. Introduced from Europe.

[Illustration: Fig. 210.]

=Common Sow-Thistle.= _Sonchus oleraceus_ L. Flowers pale yellow;
achenes reddish brown, linear, oblanceolate, 3 mm. long, flattened
extremities blunt, 5 uneven wrinkled ridges on each side. Introduced
from Europe.

[Illustration: Fig. 211.]

=Red-Seeded Dandelion.= _Taraxacum erythrospermum_ Andrz. Achene bright
red or red reddish brown, flattened, oblanceolate, 3 mm. long, 1 mm.
wide or less, the red beak 1 mm. long, prickles often extending nearly
to the base along twelve vertical ribs, the achenes narrower, shorter,
much darker in color, with prickles extending farther down the ribs, the
short beak longer; the plant is earlier, often smaller, when compared
with the other species.

Doubtless this is more common than has been reported, having been
overlooked. Introduced from Europe.

[Illustration: Fig. 212.]

=Dandelion.= _Taraxacum officinale_ Weber. _Taraxacum Taraxacum_ (L.)
Karst. Flowers yellow; achenes dull light to dark brown, flattened
oblanceolate, thread-like beak two to three times as long as the achene,
the stout colored beak 0.5 mm. long. The most conspicuous character of
the achenes lies in the barb-like-toothed edges and ridges of each of
the simil