Stem much branched, mostly buried and rooting at nodes, ascending at tip, 2-3 mm. diam., glab., the plant us. forming a lfy mat up to c. 10 cm. diam. Lvs crowded, ± appressed to ground; lamina almost fleshy, 10-25×6-15 mm., narrow- to broad-ovate, rather regularly shallowly crenate, glab. except on margins and underside of midrib; petiole c. ═ lamina, narrow, channelled, with some long hairs. Peduncle erect, us. < 12 cm. long, hairy. Bracts in 1-3 pairs, us. subentire with marginal hairs. Pedicels as many as bracts or fewer, > fls, clad in long tapering hairs. Calyx 6-7 mm. long in fl., split anteriorally almost to base, the other clefts us. shorter; lobes c. 2 mm. wide, obtuse or posterior ones retuse, sparsely hairy on margins and occ. towards inflated base. Corolla c. 1·5 cm. diam., glab. outside. Capsule sts > calyx.

DIST.: N. Known only from Kaimanawa Range and central mountains of Volcanic Plateau.

Type locality: Tongariro, herb-field c. 4800 ft. Type: BD 82462 D, A. P. Druce, Nov. 1944.

Following the keys of Hooker and Cheeseman plants belonging to this sp. have us. been placed (e.g. in Herb. Cheeseman) with O. colensoi, from the type of which they differ materially in almost glab., subcoriac. lvs and unevenly divided calyx with broad obtuse to retuse lobes; O. vulcanica never grows as large as does O. colensoi and even in the largest plants it is extremely rare to find as many as 3 floral bracts at a node. Affinities are rather with O. caespitosa. Glandular hairs appear to be absent.