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(corn mayweed, or scentless mayweed), a genus of annual and biennial odorless herbs of the family Compositae. The genus is closely related to the genus Matricaria (matricary) but differs in its greater leaf dissection and its larger heads (1.5–6 cm in diameter). The achenes have short pappi and one to three somewhat cartilaginous, thickened longitudinal ribs. There are about 30 species, distributed in the northern hemisphere. The USSR has 22 species. T. inodorum (formerly Matricaria inodora), imported into Russia from North America, grows in meadows, in fields, and along roads.