Part 4 (1/2)

NETTLE FAMILY. URTICACEAE.

[Ill.u.s.tration: Fig. 30.]

=Slender Nettle.= _Urtica gracilis_ Ait. Achenes compressed, lens-shaped, ovate, rarely oval, faces similar, smooth, dull and grayish brown, .9-1.1 mm. long. Native of this country. Compared with U. dioica, this achene is thinner and shorter. Prominent in low pastures.

BUCKWHEAT FAMILY. POLYGONACEAE.

[Ill.u.s.tration: Fig. 31.]

=Knot-Gra.s.s.= _Polygonum aviculare_ L. This door-yard weed is in no sense a gra.s.s. Achenes unequally 3-sided, ovoid, acute, angles obtuse, surface, dull, light to dark reddish brown, finely granular and striate lengthwise. 1.8-2.2 mm. long, usually with the remains of calyx attached. Native of this country. Common about door-yards.

[Ill.u.s.tration: Fig. 32.]

=Wild Buckwheat.= _Polygonum Convolvulus_ L. Achenes dull, jet-black, equally 3-sided, elliptical to obovoid, minutely granular often with faint longitudinal striation, the faces often more or less concave, the angles rounded, 2.5-3.5 mm. long, sometimes with the remains of calyx attached. Introduced from Europe. Often climbing up corn stalks.

[Ill.u.s.tration: Fig. 33.]

=Erect Knotweed.= _Polygonum er.e.c.t.u.m_ L. Achenes dull, light to dark brown, unequally 3-sided, ovoid or rhombic, finely granular and striate lengthwise, the faces sometimes concave, the angles rounded, 2.5-3 mm.

long, sometimes with the remains of calyx attached. Native to this country. Of little account.

[Ill.u.s.tration: Fig. 34.]

=Smart-weed.= _Polygonum Hydropiper_ L. Achene dull, granular, light to dark reddish brown, lenticular, acutely and narrowly or broadly elliptical, or 3-sided, apex acute, concave on the sides, angles obtuse, 2-3 mm. long, sometimes with the remains of the dotted calyx attached.

Introduced from Europe. Wet land.

[Ill.u.s.tration: Fig. 35.]

=Dock-leaved or Pale Persicaria.= _Polygonum lapathifolium_ L. Achene s.h.i.+ning, dark to chestnut brown, 2-2.2 mm. long, flattened, circular to broadly ovate with abruptly pointed apex, the base obtuse or bearing the remains of the thin calyx. Introduced from Europe. Low wet places.

=Sh.o.r.e Knotweed.= _Polygonum littorale_ Link. So far as the achenes are concerned, they are identical with those of P. aviculare above described. Native of this country. On hard or thin places, especially when newly graded.

[Ill.u.s.tration: Fig. 36.]

=Pennsylvania Persicaria=, _Polygonum Pennsylvanic.u.m_ L. Achene s.h.i.+ning, jet-black, flattened, surface very slightly uneven and granular nearly circular with a short abrupt apex, edge rounded, 2.5-3 mm. long, often bearing the remains of the calyx. Native to this country. Occasional in annual crops.

[Ill.u.s.tration: Fig. 37.]

=Lady's Thumb.= _Polygonum Persicaria_ L. Achene s.h.i.+ning, jet-black, surface finely uneven, much flattened with rounded edges or with 3 nearly equal concave faces, the edges faintly angled along the center, broadly ovate, base obtuse or bearing a portion of the calyx, apex abruptly pointed, 2-2.3 long. Introduced from Europe. Waste places and stubble ground.

[Ill.u.s.tration: Fig. 38.]

=Climbing False Buckwheat.= _Polygonum scandens_ L. Achene black, s.h.i.+ning, in cross-section sides flat or concave, corners rounded, obovate, in vertical outline sides rounded to an obtuse apex, from rounded sides to base slightly concave, base acute, 3.5-4 mm. long when freed from the persistent base of the calyx. Woods and shady places. Not prominent as a weed.

[Ill.u.s.tration: Fig. 39.]

=Sorrel. Sour Dock.= _Rumex Acetosa_ L. Calyx-wings broadly ovate or orbicular, heart-shaped 3.5-4.5 mm. long, achene s.h.i.+ning, with 3 equal sides, broadly oval, both ends abruptly pointed, the thin edges usually lighter colored than the dark brown or black convex faces, 1.5-2 mm.

long. Introduced from Europe. Not common.

[Ill.u.s.tration: Fig. 40.]