D. Bridson, J. Degreef, & M. Thulin (2006) Rubiacae. Flora of Somalia 3: 61-110
Plants trees, shrubs, herbs, or climbers, sometimes spiny. Leaves opposite or whorled, entire, stipulate; stipules inter- or intrapetiolar, sometimes leaflike. Inflorescences usually terminal or axillary, rarely of solitary flowers. Flowers usually bisexual, rarely unisexual, radially symmetric or almost so; calyces 4-5-lobed, sometimes united into a tube at the base, sometimes reduced to a truncate rim; corollas tubular to rotate, usually 4-5-lobed, the lobes mostly touching or twisted, rarely overlapping; stamens attached to the corollas, alternating with the corolla lobes, anthers usually dehiscing longitudinally; ovaries usually inferior, rarely half inferior or even superior, usually 2(-5)celled, ovules 1-many per cell, placentation axile, basal, apical or, rarely, parietal; styles 1, usually narrow but sometimes modified distally into a globose, cylindrical, or club-shaped pollen presenter, rarely divided almost to the base. Fruits capsules, berries, or drupes or dry and indehiscent or splitting into mericarps.
Rubiaceae include about 600 genera and 1000 speices. It is most abundant in tropical and subtropical regions.