The princewood (Exostema caribaeum) belongs to the Rubiaceae (the Madder family). It is small evergreen tree that is naive to southeastern North America, Central America and northern South America. This tree grows in arid coastal thickets and woodlands, and up to a height of 3-8 m. The bark is grayish and develops horizontal fissures with age. The leaves are arranged oppositely, up to 12 cm long, and lanceolate with slightly undulating but entire leaf margin. The flowers are white, salverform in shape, and produces an extended tube that is about 5 cm long with five elongated lobes. The fruit is a brown capsule. The leaves and bark are bitter, and formerly the plant was used as a substitute for quinine to treat fevers, including malaria.