Aerial stem-parasitic shrubs, often robust, with epicortical runners bearing secondary haustoria. Leaves mostly opposite, sometimes displaced; venation pinnate. Inflorescences axillary, primarily a raceme of decussate pairs of pedunculate dichasia (triads), sometimes variously reduced (see below); bracts single under each flower, not enlarged to form an involucre. Fruit ellipsoid to globular, usually with a persistent nipple-like style base.
Asia-Tropical:, New Guinea ‒ present from Thailand and Peninsular Malaysia eastwards and southwards to New Guinea, Australia, New Caledonia and New Hebrides: present northwestern Malesia: present
Four species distributed from Thailand and Peninsular Malaysia eastwards and southwards to New Guinea, Australia, New Caledonia and New Hebrides. In Malesia 3 species, 1 in northwestern Malesia and 2 in New Guinea.
The plesiomorphic inflorescence state for the genus is an axillary raceme of uniformly spaced opposite pairs of triads. Simpler inflorescences are derived by reduction, and occur primarily as infraspecific rather than interspecific variations. The inflorescence is often subumbellate, and the triads may be reduced to single flowers so that the inflorescence may appear to be a simple raceme or even a 2-flowered simple umbel ().
Danser (1931) included Decaisnina in Amylotheca, which was therefore more broadly circumscribed than it is here. Amylotheca is closely related to Decaisnina:, which is probably the least specialized genus in the group. The major difference is in the corolla, which is essentially choripetalous in Decaisnina, although usually with the petals coherent at the base into a short tube, and distinctly gamopetalous to the middle or higher in Amylotheca. For further discussion of generic relationships see