unded by
a broad wrinkled wing-margin or hem. The concave side bears a slender
vertical ridge (raphe) for two-thirds of its length; the convex side
bearing fine, short ridges. Before escaping from the pods, the small end
of the seed contains a cluster of spreading silky hairs (coma) 2-3 cm.
long. Native of this country. Often troublesome and conspicuous in light
soil, occasionally becoming small, pale, with slender branches and
dying.

[Illustration: Fig. 141.]

=Black Swallow-wort.= _Cynanchum nigrum_ (L.) Pers. _Vincetoxicum
nigrum_ Moench. Smooth pods of the vine about 5 cm. long; seeds brown
when dry, much flattened, concave, obovate, 6-8 mm. long, nearly
surrounded by a wing margin or hem, the small end truncate. The concave
side bears a slender vertical ridge (raphe) for over half its length,
both sides bearing fine short ridges. Before escaping from the pods, the
small end of the seed contains a cluster of spreading silky hairs.
Introduced from Europe; not yet common, but it is persistent where once
started.

MORNING GLORY FAMILY. CONVOLVULACEAE.

[Illustration: Fig. 142.]

=Small Bindweed.= _Convolvulus arvensis_ L. Color of seeds dull dark
brown, coarsely roughened, oval, 3-4 mm. long, one face convex, the
other face sloping to the edges from a broad, central ridge, becoming
mucilaginous when soaked in water. Introduced from Europe. Seldom, if
ever, seeding in Michigan. On dry, poor land.

[Illustration: Fig. 143.]

=Hedge or Great Bindweed.= _Convolvulus sepium_ L. Pod nearly globose,
about 8 mm. in diameter, usually covered by the bracts and calyx; seeds
dull black or dark brown, roughened, oval, about 5 mm. long, one face
convex, the other face sloping to the edges from a central ridge. Native
to this country. Seldom seeding in Michigan. On low land.

[Illustration: Fig. 144.]

=Field Dodder.= _Cuscuta arvensis_ Beyrich. A pale yellow leafless
parasitic vine; seeds dull, yellowish brown, minutely pitted,
considerably resembling those of red clover, broad oval, ovoid or
spherical, .7-1 mm. long, one side rounded the other often with two flat
surfaces terminating in a ridge. Not uncommon with alfalfa.

[Illustration: Fig. 145.]

=Flax Dodder.= _Cuscuta Epilinum_ Weihe. Stems very slender, yellow or
red, a parasitic vine; seeds dull, yellowish to dark brown, minutely
pitted, nearly spherical, oval, ovoid, 1-1.5 mm. long. Introduced from
Europe.

[Illustration: Fig. 146.]

=Clover Dodder.= _