4. Hydnophytum ovatum Miq. — Fig. 5; Map 1

Hydnophytum ovatum Miq. (1869) 257; Becc. (1885) 143, t. 32: 8–14. — Type: Teysmann & de Vries 20 (lectotype selected here L; CAL not seen), Indonesia, Moluccas, Ternate, Mar. 1860.

Tuber oblong to globose, dark brown, without ridges or spines. Stems several, branched to 70 cm; internodes 1.5–5 by 0.1–0.5 cm, rounded to subterete. Leaves sessile. Lamina ovate to orbicular, 1.6 by 1.3 to 3.6 by 3.2 cm; apex obtuse; base truncate to cordate; midrib diminishing rapidly, prominent near base; veins 4 or 5; leathery in texture, drying reddish brown. Stipules triangular, to 0.2 by 0.2 cm, caudate, caducous. Inflorescence a mass of tightly grouped sockets in a swollen node. Bracts papery to hairy, to 2 mm long. Flowers [3] heterostylous. Calyx to 1 mm entire. Corolla to 6.5 mm; tube 5 mm; lobes triangular to 1.5 mm; a narrow band of very short hairs at mouth of tube. Short-styled flowers with anthers exserted; pollen 63 (60–65) µm, brochi 1.5 µm; stigma bifid, below mouth of tube. Long-styled flowers with anthers within mouth of tube, to 1 mm long; pollen 48 (44–53) µm, brochi 1 µm; stigma exserted. Fruit globose, to 5 mm, calyx remains prominent. Pyrenes obovoid, 2 by 1.2 mm, rounded at apex.

Ecology & Habitat — Forest, 1 200–1 500 m. Tuber inhabited by ants.

Distribution — North Maluku Province (Ternate and Tidore Islands).

Conservation status — Vulnerable (VU) under criteria D2. Known from two small and adjacent volcanic islands this taxon may be prone to sudden habitat fluctuations.

Note — The inflorescence is composed of several peduncular sockets each of which produces a succession of flowers, and which together form a large swollen mass at the nodes. Where a branch arises at a fertile node, these sockets lie to each side of the branch, and above it. It is distinguished from H. spathulatum [5] by its leaf shape. It is restricted to the volcanic islands of Ternate and Tidore.