Driessenia phasmolacuna (Sonerileae, Melastomataceae), a new species from Batang Ai, Sarawak, Borneo

Driessenia phasmolacuna (Sonerileae, Melastomataceae), a new species from Batang Ai, Sarawak, Borneo

A new species, Driessenia phasmolacuna C.W. Lin, from Batang Ai, southwestern Sarawak, is described and illustrated. It belongs to a distinct group of Driessenia that have subequal or unequal leaves in each pair, often congested cymose inflorescence with many tiny flowers. Morphologically, it is similar to D. sessiliflora, but differing in its stem being 4-winged (vs. wing absent), larger laminas 18–22×5–7 (vs. 13–14.5×3.7–5) cm, much longer pedicel 3–5 (vs. 0.1–0.5) mm long, shorter bracts ca. 0.3 (vs. 1–1.5) mm long, pedicel 3–5 (vs. 0.1–0.5) mm, petal white (vs. yellowish) and ovary subequal in length to hypanthium (vs. exceeding hypanthium by one fourth) in fruit. Detailed comparison of the new species with five phenetically similar species are also presented.