S. Nazimuddin and M. Qaiser. Flora of Pakistan 148: 5-8
Plants tree or shrubs, usually with whorled branches. Leaves usually whorled. Inflorescences paniculate or corybose terminal cymes. Flowers salviform; calyces short, united, 5-lobed, without glands inside; corollas united, 5-lobed, tube hairy only at the mouth; stamens 5, included, inserted on the corolla tube, anthers lanceolate; disc of various shapes, annular, truncate, or lobed, rarly absent; ovules many per carpel, multiseriate; styles filiform, stigmatic regions short. Follicles 2, cylindrical; seeds many, oblong or linear, usually hairy.
Alstonia comprises about 30 species and is native in Africa, Asia, Australia, and Polynesia. It is represented in Pakistan by two cultivated species.