Belongs within: Loganiaceae.
Geniostoma is a genus of about fifty species of small trees and shrubs found in south-east Asia and Australasia. Species have been divided between two sections, with the species G. umbellatum (known only from Guadalcanal in the Solomon Islands) set apart from others by its unusually large stipules. The New Guinean G. randianum bears leaves inserted on distinct nodal swellings (Conn 1995).
Characters (Conn 1995): Small shrubs to small trees, rarely scrambling to semi-climbing. Branches terete, quadrangular or four-winged, variously hairy or glabrous. Stipules mostly intrapetiolar. Leaves simple, opposite, more or less petiolate or sessile. Inflorescences terminal or axillary, ramiflorous or cauliflorous, uniflorous, dichasial or pleiochasial, often umbelliform or glomerulate. Calyx, corolla and androecium pentamerous. Sepals united at base; inner surface of calyx often with colleters at base; lobes imbricate in bud, margin mostly fimbriate. Corolla campanulate to rotate, white; outer surface glabrous to shortly hairy; inner surface glabrous to densely pilose; lobes imbricate or contorted in bud. Stamens alternipetalous, attached to mouth of corolla tube, exserted, usually recurved after anthesis, glabrous or hairy; filaments mostly short; anthers bilocular, introrse, connective often extended to form apical appendage. Pistil variously hairy or glabrous; ovary bilocular; placentas axile with many amphitropous ovules; style mostly short; stigma clavate, ellipsoid to globular, sometimes more or less oblong, about as large as ovary. Capsule ellipsoid to globular, sometimes more or less oblong, rarely flattened-ellipsoid, bivalved, septicidal to subseptifragal, maturing to green, with or without a black-purple tinge, usually becoming brown-black when over-mature. Seeds embedded in juicy orange or red pulp, numerous, ellipsoid to subglobular, intruded on hilar side; surface mostly minutely papillose to areolate, brown to black, endosperm thick, fleshy; embryo small, straight.
<==Geniostoma Forster & Forster 1776A61
| i. s.: G. ligustrifolium Cunn. 1839A61 (see below for synonymy)
|--G. sect. GeniostomaC95
| |--G. antherotrichum Gilg & Benedict 1916C95
| | |--G. a. var. antherotrichum [incl. G. arfakense Kan. & Hat. 1942]C95
| | `--G. a. var. archboldianum (Merr. & Perry) Conn 1980 [=G. archboldianum Merr. & Perry 1942]C95
| |--G. leenhoutsii Conn 1980C95
| |--G. randianum Merr. & Perry 1942 [incl. G. obtusum Merr. & Perry 1942]C95
| |--G. rupestre J. R. & Forster 1776 [incl. G. stenophyllum Gilg & Benedict 1916]C95
| | |--G. r. var. rupestre (see below for synonymy)C95
| | |--G. r. var. crassumL97 [=G. ligustrifolium var. crassum Cheeseman 1897A61]
| | |--G. r. var. glaberrimum (Benth.) Conn 1980 [=G. crassifolium var. glaberrimum Benth 1857]C95
| | |--G. r. var. moluccanum (Bl.) Conn 1980 (see below for synonymy)C95
| | |--G. r. var. rouffaeranum Conn 1980C95
| | `--G. r. var. solomonense Conn 1980C95
| |--G. trichostylum Conn 1980C95
| `--G. weinlandii Schumann in Schumann & Lauterbach 1905 [incl. G. acutifolium Hiern 1909]C95
`--G. (sect. Macrostipulare) umbellatum Conn 1980C95
Geniostoma ligustrifolium Cunn. 1839A61 [=G. rupestre var. ligustrifoliumMM04; incl. G. ligustrifolium var. major Cheeseman 1906A61]
Geniostoma rupestre var. moluccanum (Bl.) Conn 1980 [=G. lasiostemon var. moluccanum Bl. 1850; incl. G. dallmannense Kan. & Hat. 1942]C95
Geniostoma rupestre J. R. & Forster 1776 var. rupestre [incl. G. acuminatissimum Gilg & Benedict 1916, G. brassii Merr. & Perry 1942, G. caulocarpum Schumann 1905, G. dasyneuron Gilg & Benedict 1916, G. psychotrioides Gilg & Benedict 1916, G. pullei Cammerl. 1924, G. schlechteri Gilg & Benedict 1916]C95
*Type species of generic name indicated
References
[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).
[C95] Conn, B. J. 1995. Loganiaceae. In: Conn, B. J. (ed.) Handbooks of the Flora of Papua New Guinea vol. 3 pp. 132–188. Melbourne University Press: Carlton (Australia).
[L97] Lange, P. J. de. 1997. Hebe brevifolia (Scrophulariaceae)—an ultramafic endemic of the Surville Cliffs, North Cape, New Zealand. New Zealand Journal of Botany 35: 1–8.
[MM04] Martin, N. A., & L. A. Mound. 2004. Host plants for some New Zealand thrips (Thysanoptera: Terebrantia). New Zealand Entomologist 27: 119–123.