Seeds of Michigan Weeds Part 13

[Ill.u.s.tration: Fig. 205.]

=p.r.i.c.kly Lettuce.= _Lactuca virosa_ L. For many years erroneously called _Lactuca scariola_. Flowers yellow; achenes dull, dark brown, mottled with black, flattened, bearing 5-7 rough, vertical ridges, interspersed by as many smaller ones; oblong, obovate, widest toward the tapering apex. 3-3.5 mm. long. Some of the leaves turn one edge up and the other down. Introduced from Europe and has proved itself a remarkable traveller.

[Ill.u.s.tration: Fig. 206.]

=Fall Dandelion.= _Leontodon autumnalis_ L. Flowers yellow; achenes light brown, 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: Fig. 208.]

=Corn Sow-Thistles.= _Sonchus arvensis_ L. Flowers yellow; achenes dull, dark reddish brown, oblong, extremities blunt, slightly flattened, bearing four coa.r.s.e, 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: Fig. 211.]

=Red-Seeded Dandelion.= _Taraxac.u.m 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, p.r.i.c.kles often extending nearly to the base along twelve vertical ribs, the achenes narrower, shorter, much darker in color, with p.r.i.c.kles 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.

[Ill.u.s.tration: Fig. 212.]

=Dandelion.= _Taraxac.u.m officinale_ Weber. _Taraxac.u.m Taraxac.u.m_ (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 similar faces, extending along the upper half. Achene, 3-4 mm. long, having twelve longitudinal ridges, 1.2 mm. wide. Introduced from Europe.

Troublesome on thin lawns.

[Ill.u.s.tration: Fig. 213.]

=Salsify. Oyster-Plant.= _Tragopogon porrifolius_ L. Flowers purple; achenes dull light brown, nearly cylindrical; apex tapering, mostly terminating in a slender beak which is often longer than the body of the achene. Achene straight or curved, 10-ribbed, 12-18 mm. long, outermost coa.r.s.ely roughened by upwardly directed, whitish, scale-like projections. Native of Europe.

=Meadow Salsify. Yellow Goat's Beard.= _Tragopogon pratensis_ L. Flowers yellow; achenes dull, light brown, nearly cylindrical, apex tapering, mostly terminating in a slender beak. Achene straight or curved, 10-ribbed, 12-15 mm. long, the inner ones of the head smooth, the outer-most coa.r.s.ely roughened by upwardly directed, whitish, scale-like projections. Introduced from Europe.

[Ill.u.s.tration: Fig. 214.]

=American c.o.c.klebur.= _Xanthium Canadensis_ Mill. Achenes or burs reddish brown, oblong, circular in section, two-beaked, about 20 mm.

long, covered with stout hooked p.r.i.c.kles. Each bur encloses two seeds.

Native of this country.

[Ill.u.s.tration: Fig. 215.]

=Spiny Clotbur.= _Xanthium spinosum_ L. Bur oblong, light brown, very slightly flattened, 10-13 mm. long, the beaks weak and small, small hooked p.r.i.c.kles 3-4 mm. long, each bur contains two seeds. Introduced from Europe.

=Broad c.o.c.klebur.= _Xanthium strumarium_ L. Bur dark brown, oval, circular in sections 12-22 mm. long, beaks stout, nearly straight, spines about 5 mm. long, surface of burs and base of spines clothed with minute hooked p.r.i.c.kles. Naturalized from Europe.