Macrosolen x tubiflorus
Glabrous. Leaves opposite; lamina ovate, 10-20 by 4-8 cm, cuneate to truncate at the base to a petiole 4-10 mm long, mostly acuminate and acute at the apex, lustrous or glossy above, dull below; venation pinnate with the midrib distinct and the main laterals visible on both sides. Inflorescences at the nodes, a raceme of 2-7 opposite pairs of flowers; axis 10-20 mm long, subtended at the base by an involucre of short broadly triangular bracts; pedicels appressed to the axis, 1-4 mm long, bracts keeled, acute, 2-3 mm long.
Asia-Tropical: Borneo present; Malaya (Peninsular Malaysia present)
Malesia: Peninsular Malaysia, Borneo.
The species shows features of both Macrosolen acunae (especially in the inflorescence and flowers) and M. formosus (especially in the leaves); it is possibly of hybrid origin, although now perhaps persisting as a stable recognizable form, and has been designated accordingly. The species can be distinguished from M. formosus by its shorter inflorescence with more flowers on crowded and more appressed pedicels, and its narrower more acute corolla with weaker wings and ridges.