Plants in this genus are evergreen trees or shrubs, which may be
deciduous or semi-deciduous. Leaves are
entire or toothed.
Inflorescences are pendulous or (rarely) erect
racemes, either , , or
cauliflorus. The has four or five lobes (with the exception of
B. asiatica, two or three), petals number between three and six. Stamens are numerous, arranged in three to eight whorls. Ovaries are two to four
locular, with two to eight ovules per locule. The fruit may be , or , and may be angled or winged. They contain one large seed. ==Species list==