mities passing vertically over the glume, two light nerves on the
palea. Native to this country.

[Illustration: Fig. 18.]

=Tall Smooth Panicum. Switch Grass.= _Panicum virgatum_ L. Achene
surrounded by two persistent shining pieces, the floret; floral glume
hard, light brown, oval or ovate-lanceolate 2.5-3.1 mm. long. Apex
obtusely pointed. Seldom troublesome, widely distributed.

[Illustration: Fig. 19.]

=Low Spear-Grass.= _Poa annua_ L. Florets straw-colored, 2.8-3.1 mm.
long, apex smooth, lower half of keel and the base of lateral nerves,
having numerous soft hairs. A low annual grass, introduced from Europe.

[Illustration: Fig. 20.]

=Flat stemmed Poa. Wire Grass. Canadian Blue Grass.= _Poa compressa_ L.
Florets lance-obovate, 2-2.5 mm. long, closely resembling those of Poa
pratensis, which see.

Palea abruptly acute. If well rubbed after threshing, the floret is
nearly smooth, otherwise it contains on the lower half numerous webby
hairs. Grain reddish brown, both ends pointed, 1-1.4 mm. long. Seldom
sown purposely. Sometimes used to adulterate Poa pratensis. In early
days this grass was called blue grass by people of New England and New
York State. Introduced from Europe.

[Illustration: Fig. 21.]

=June Grass. Kentucky Blue Grass.= _Poa pratensis_ L. Florets
ovate-lanceolate, acute 3-4 mm. long, with three equal sides when seen
in transverse section, nearly smooth, if severely rubbed in threshing,
otherwise the floral glume is thickly webbed at the base; palea
acuminate, grain light brown, elliptical, both ends usually pointed
1.2-1.4 mm. long, in cross sections with three equal sides, one of which
has a shallow vertical groove. Compare with Poa compressa. Introduced
from Europe.

[Illustration: Fig. 22.]

=Rye.= _Secale cereale_ L. Grain light brown, 6-8 mm. long, elliptical,
base acute, apex obtuse and rounded, in cross section the back somewhat
acutely rounded, the opposite side with a narrow vertical groove,
surface more or less irregularly wrinkled. Introduced from Europe. A bad
weed in wheat fields.

[Illustration: Fig. 23.]

=Pigeon-Grass. Yellow Foxtail.= _Setaria glauca_ (L.) Beauv.
_Chaetochloa glauca_ (L.) Scrib. Spikelets light to dark brown, 2.5-3
mm. long; after threshing or much rubbing consisting of each a grain and
two firm coverings, known as a floral glume which covers the sides of
the somewhat depressed palea, oval, apex slightly 3-toothed, rounded
side strongly arched, so