CORN COCKLE, Agrostemma
githago L. 1, plant in flower; 2, seed pod enclosed
by the ribbed calyx; 3, seed. Winter annual, reproducing
by seed. Taprooted, shallow. Stems rough, hairy, erect, 2
to 3 feet (60 to 90 cm) tall, swollen at joints, branching slightly. Leaves
opposite and joined at base, slender, hairy. Flowers large, purple,
with narrow, green sepals longer than colored petals. Seed pod
holding several seeds, enclosed in a 10-ribbed urnlike calyx. Seeds
black, about 1/8 inch (3 mm) in diameter, triangular, covered with rows
of sharp tubercles. Seeds poisonous and therefore highly objectionable
in grain used for milling or feed. Found especially on cultivated
land and in association with fall-sown grain crops.