Soliva sessilis
puncture vine, Tribulus terrestris
three-cornered jack, Emex australis
A burr from one of these weeds.
Centaurium, sensu stricto
Centaurea, a genus in the Asteraceae containing species sometimes called centaury
Gyrandra, a genus in Gentianaceae, formerly included in Centaurium, with species commonly called centaury
Cheirolophus crassifolius, a species in the Asteraceae commonly known as Maltese centaury
Schenkia, a genus in Gentianaceae, formerly included in Centaurium, with species commonly called centaury
Zeltnera, a New World genus in Gentianaceae, formerly included in Centaurium, with species commonly called centaury
Sabatia, a New World genus in the Gentianaceae containing species sometimes called centaury