CYRTOSPERMA BOUGAINVILLENSE
PROTOLOGUE:
Cyrtosperma bougainvillense A.Hay, published in Blumea 33: 441 (1988), with Fig. 6.
Type: R. Schodde & L. Craven 3837, Papua New Guinea, North Solomons Province, Bougainville Island, Maide Gorge, lower southern slopes of the Lake Loloru crater, about 15 miles north of Buin, 14 August 1964 (holotype CANB; isotypes A, K, L, LAE). Hay's diagnosis: differs from C. merkusii in the more or less flat spathe, the twisted stony seed, the vermilion stigma and the glaucous spadix.²
SYNONYMS:
HOMOTYPIC SYNONYMS: N/A
HETEROTYPIC SYNONYMS: N/A
ACCEPTED INFRASPECIFICS: N/A
DISTRIBUTION:
Solomon Islands: Solomon Is. (Bougainville).¹
DISTRIBUTION NOTE: Restricted to Bougainville: Panguna, Kieta, Kapikavi and Arawa. Locally abundant there yet unrecorded elsewhere in the Solomon chain; a fragmentary 1931 Waterhouse specimen from "Iru (Mt. area), Siwai" may belong here.² All records are from 1931–1967.⁴
SPECIES DESCRIPTION:
Robust, usually solitary herb 1–2.4 m tall; rhizome often long and creeping. Leaves 2–5, sagittate; petioles prickly, green mottled with white; spines slender, without conspicuously broad bases, slightly curved, scattered or tending to short comb-like clusters; geniculus up to 14 cm long; sheath papery-fibrous, about a fifth the length of the petiole; posterior lobes 40–75 cm long and 20–30 cm wide, the tips not acuminate; anterior lobe 35–50 cm long and to c. 60 cm wide, with spreading costae.²
INFLORESCENCE:
Peduncle to 2 m long, usually shorter than the petioles, prickly. Spathe blackish purple to almost white, broadly lanceolate, to 27 cm long and 6.5 cm wide, widely open to the base, somewhat deflected from the spadix and not shielding it from the side, the upper part sometimes falling forward over the spadix. Spadix stipitate for c. 6 mm, the insertion running c. 1 cm up the spathe; fertile part to 11.5 cm long and 1.6 cm wide in flower, purplish to glaucous-blue. Flowers hexamerous; anthers dirty yellow, exserted from the tepals at male anthesis; receptive stigmas bright scarlet; ovules one or two. Fruiting spadix becoming horizontal to pendulous, dark bluish to black. Fruit obpyramidal, c. 8 by 8 mm, orange, truncate at the apex. Seed tightly curved over on itself; seed coat very thick, stony, somewhat rough.²
ECOLOGY:
Montane rainforest and regrowth in moist gullies at 600–2,000 m on the actively volcanic, copper-bearing island of Bougainville; possibly restricted to cupriferous soils.² Records at 610–884 m.⁴
DISTRIBUTION MAPS:
Hay 1988 Fig. 3.
ETYMOLOGY:
Of Bougainville, the island to which it is confined.
NOTES:
1. The seed is distinctive: campylotropous like the rest of the genus, but with the micropylar and chalazal ends overlapping so that it is helical, and the funicle appears to enter through a hole in the side.² With the heavily ornamented seed coat and the exserted anthers it sits closest to the lowland C. merkusii.²
2. The bright scarlet receptive stigmas and glaucous-blue spadix are unique in the genus.²
3. Bougainville's history since the 1960s has left the species uncollected for decades, and no photograph of a living plant was found.⁴ ⚠
STORY:
STORY TITLE: The species an island closed the door on
It is the only montane Cyrtosperma, growing between 600 and 2000 m where every other species in the genus keeps to lowland swamp and stream sides. Its seeds are helically twisted and stony, a form found nowhere else in the genus.
Almost everything known about it was collected before 1967. Bougainville's mining and political history then made the island effectively unreachable for botany, and GBIF holds no record of the species since. No modern photograph exists.
Fifty-nine years on, Cyrtosperma bougainvillense is known exactly as well as it was on the day the last collector left.
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Cyrtosperma bougainvillense.
2. Hay, A. 1988. Cyrtosperma (Araceae) and its Old World allies. Blumea 33: 427–469 — protologue, p. 441.
3. iNaturalist: Cyrtosperma bougainvillense
4. GBIF occurrence download for Cyrtosperma, 2026-09-05 (19 records)