4. Matricaria Linnaeus, Sp. Pl. 890. 1753; Gen. Pl. ed. 5. 380. 1754; Grierson in P.H.Davis, Fl. Turk. 5: 293. 1975; Kay in Tutin et al., Fl. Europ. 4: 165. 1976. pro parte; K. Bremer & Humphries in Bull. Nat. Hist. Mus. Lond. (Bot.) 23 (2): 153. 1993; K. Bremer, Asteraceae: 476. 1994.
Chamomilla Gray, Nat. Art. Brit. Pl. 2: 454.1821; Kay in Tutin et al., l. c. 167. 1976.
Annual herb with alternate, 2-3-pinnatisect leaves. Capitula heterogamous and radiate or homogamous and disciform, solitary terminal. Involucre depressed hemispherical, phyllaries 2-3-seriate, with membranous margins. Receptacle conical to subulate, hollow, glabrous. Ray-florets female, fertile, with white ligules. Disc-florets yellow, with 4-5-lobed corolla tube swollen in fruit, lobes spreading, rarely with resin canals; style branches truncate. Cypselas oblong-cylindric, slightly dorsiventrally compressed, thinly 5-ribbed on adaxial side, ribs with myxogenic cells. Pappus absent or a short corona or occasionally, especially in ray-florets, an adaxial auricle.
A small genus of 7 species (Bremer & Humphries 1993), widely distributed in Europe, Middle East, temperate Asia, N. Africa and N. America; some are widespread as weeds in S hemisphere. Represented by two species in our flora.
This genus is often confused with Tripleurospermum, from which it is easily distinguishable by its adaxially 5-ribbed achenes.
