The aroids of Borneo
H. N. Ridley, then Director of the Singapore Botanic Gardens, published this floristic treatment of the Araceae of Borneo in 1905, drawing on his own 1903 collecting trip to Sarawak alongside earlier material from Beccari, Haviland, Korthals, Motley, Grabowski, and Hallier. The paper serves as a comprehensive checklist of aroid species known from the island at that time, while simultaneously describing eighteen new species and correcting taxonomic confusions arising from the widespread practice of describing aroids from leaves alone.
Summary
Ridley’s central concern is the taxonomic instability of Bornean aroids, which he attributes to the “very bad habit” of botanists and gardeners who described species from leaves only, a practice he considers “quite worthless” given the extreme variability in leaf form and venation within the family (p. 169). Many Bornean aroids possess ornamental foliage and had been introduced into cultivation under inadequate names, compounding the confusion. Ridley addresses this by grounding his determinations in floral and fruiting characters wherever possible, and by explicitly flagging species he could not resolve—such as Schismatoglottis Beccariana, which he states he “failed to recognise” (p. 180).
The paper is organised by genus and covers eighteen genera ranging from the aquatic Cryptocoryne to the climbing Pothos. The most heavily treated genera are Homalomena (including both the Euhomalomena and Chamaecladon sections) and Schismatoglottis, each of which yields multiple new endemic species from Sarawak. Ridley’s own 1903 collections from Matang, Bidi, and Bau in Sarawak, together with Haviland’s earlier Sarawak material, form the backbone of the new descriptions, while Beccari’s Sarawak collections and Korthals’s South Bornean specimens provide the comparative framework. Several species are noted as introduced garden plants of uncertain native status, such as Colocasia antiquorum and Alocasia indica, which Ridley treats as cultivated rather than wild (pp. 178–179).
A recurring theme is the endemicity of Bornean aroids, particularly in Cryptocoryne and Homalomena, where Ridley marks numerous species as restricted to Sarawak. He also draws attention to the gap between what is known and what remains to be collected, opening the paper with the observation that his list “represents doubtless but a small portion of those which will eventually be found by collectors” (p. 169).
Key Findings
- Ridley describes 18 new species across seven genera: Cryptocoryne grandis, Arisaema umbrina, Homalomena sarawakensis, H. borneensis, H. havilandi, H. fasciata, H. paucinervia, H. intermedium, H. crassinervia, H. lancea, Schismatoglottis multiflora, S. caulescens, Scindapsus rupestris, S. havilandi, Rhaphidophora migrescens, R. elliptica, R. fluminea, and Pothos longus (pp. 169–188).
- Cryptocoryne is identified as attaining its “maximum development” in Borneo, with at least nine species recorded, most of them endemic to Sarawak jungle streams (pp. 169–171).
- Pothos longus (Haviland 934, four miles from Kuching) is noted for its exceptionally long spathe (9 inches) and spadix (6 inches), and for perianth lobes with “very narrow elongate tops” hardly one-fourth as wide as they are long (p. 188).
- Schismatoglottis multiflora (Ridley 11582, Matang) is described as “abundant” in stream rocks and “remarkable for its long spadix and very numerous flowers,” with a 3-inch male spadix and no appendage of barren flowers (p. 181).
- Homalomena fasciata (Ridley, Bidi Woods, fl. Oct. 1903) was brought alive to Singapore and flowered in the Botanic Gardens, confirming its identity (p. 174).
- Alocasia Lawii is recorded as “common on limestone rocks” in both Borneo and the Malay Peninsula, with Ridley noting that Beccari “could hardly have failed to find it” despite its absence from Beccari’s published list (p. 178).
Conclusion
Ridley’s definitive takeaway is that Borneo’s aroid flora is far richer and more endemic than previously recognised, but that reliable taxonomy of the group is impossible without floral material. His paper simultaneously expands the known species count substantially and establishes a methodological standard—insisting on spathe, spadix, and fruit characters—that would guide subsequent revisions of the family in Malesia.
Context
- Ridley held the position of Director of the Singapore Botanic Gardens (1887–1918) and was the pre-eminent living-botanist of the Straits Settlements; his 1903 Sarawak trip was conducted in that official capacity, and several of his new species were named after colleagues and collectors (Haviland, Beccari, Motley, Lob).
- The primary archival sources are the herbarium collections of the Singapore Botanic Gardens (Ridley, Haviland, Beccari, Bartlett numbers) and the Kew herbarium (Korthals, Motley, Grabowski, Hallier material), with Engler’s Malesia (1896–1911) serving as the principal comparative reference.