Staminal tube zygomorphic

Only species of Allantoma, Grias, Gustavia, and Cariniana have staminal tubes. The frist three genera possess actinomorphic androecia while those of Cariniana are zygomorphic. The zygomorphy of species of Cariniana differs in that one side of a staminal is prolonged whereas in all other zygomorphic-flowered genera the prolongation departs from a staminal ring which is a donut-shaped area surrounding the style from which the stamens arise. The staminal tube can be scarcely to well-developed and the prolongation can be barely noticeable (e.g., in Cariniana parvifolia to conspicuous (as in most other species of the genus).