6. Tripleurospermum Schultz-Bip, Tanacet. 31. 1844; E. Hossain in P.H. Davis, Fl. Turk. 5: 295. 1975 ; Podlech in Rech. f., Fl. Iran. Comp. IV. 158: 73. 1986; K. Bremer & Humphries in Bull. Nat. Hist. Mus. Lond. (Bot.) 23(2): 155. 1993; K. Bremer, Asteraceae: 478. 1994.
Chamaemelum Vis., Giorn. Bot. Ital. 1: 33. 1844, non Miller (1754).
Annual or perennial, ± glabrous to sparsely hairy herbs with alternate, 1-3-pinnatisect leaves. Capitula discoid, radiate or disciform, hetero- or homogamous, pedunculate, solitary or in corymbs. Involucre ± hemispherical, phyllaries 2-5-seriate, imbricate, scarious-margined. Receptacle glabrous, convex to elongate conical or hemispherical. Ray-florets female, mostly white or pale-pink, ligulate, rarely tubular or eligulate. Disc-florets bisexual, with 5-lobed corolla tube, each lobe with a reddish or sometimes brown-black gland-like resin sac at tip. Cypselas mucilaginous or not, triquetrous, oblong or obpyramidate, with single adaxial or a pair of lateral thick, sometimes thin, whitish ribs, often rugose or tuberculate anteriorely and between the ribs, 2 (-3-5), glandulose at the apices. Pappus absent or scarious coronate, crenulate or occasionally auricle 3-lobed.
A difficult genus of c. 38 species, distributed mainly in Europe and temperate Asia, a few species occur in N. America and N. Africa (Bremer & Humphries, l.c. 1993). Represented in Pakistan by 3 species.
This genus, treated under Matricaria by some authors, is characterized by 3-ribbed cypselas bearing 2 abaxial resinous glands which are absent in Matricaria.