Asteraceae
Flowers grouped into heads Asteraceae
Involucral bracts of the female heads or of the outer florets enclosing the fruit(s) at maturity and forming a burr (Fig. 42)
Burrs with hooked appendages
Burrs solitary or few together in the axils of alternate leaves, each burr containing 2 fruits Xanthium
Stems with 3-branched yellow spines at the base of the leaves. Leaves narrow-elliptic to lanceolate, up to 8 cm long, entire or 3-lobed, white tomentose underneath. Burrs 10–12 mm long, pubescent, spines numerous, c. 3 mm long. Herb up to 1 m high. Widespread. Weed of cultivation, pastures and waste places. Introd. from S. America. Fl. most of the year. Bathurst Burr Xanthium spinosum
Stems without spines