A botanical excursion to Pulau Adang
H. N. Ridley, C.M.G., F.R.S., Director of the Singapore Botanic Gardens, published this field report in 1912 documenting a botanical collecting expedition to the Pulau Adang island group in April 1911. The article presents the first systematic investigation of the flora of these outlying islands west of Lankawi and Terutau, and argues that their plant communities align with a Malayan rather than a southern Siamese floristic affinity.
Summary
Ridley and a party including H. C. Robinson, Mr. Seemund, Dr. Hanitsch, and zoological collectors sailed aboard the Seabelle from Kuala Lumpur via Penang, reaching the islands on 20 April. Over several days they worked across Pulau Rawi, Pulau Adang, Pulau Butong, Pulau Nipis, and Pulau Tengah, collecting from seashore, rocky slopes, low swampy woods, and a hill ridge reaching approximately 1,000 feet. The expedition also extended to the Lankawi islands, where the party visited Telayah Tujoh (the “Seven Wells”), a rocky stream basin at roughly 1,000 feet altitude that served as a local Malay picnic site (pp. 45–48).
The central analytical contribution of the article is Ridley’s floristic assessment. He observes that the Adang group’s flora is markedly different from that of the nearby Lankawi islands, showing a preponderance of Malayan Peninsula forms—Agelaea, Urophyllum, Lasianthus, various Dipterocarpeae and Anonaceae—over the southern Siamese elements one might expect given proximity to the Thai border. He draws a parallel with the Pulau Song-Song group off Kedah, which likewise lacks southern Siamese plants, and notes a further affinity with the Andaman Islands, which share a Malayan flora unconnected to the Siamese element (pp. 48–49). At the same time, the seashore assemblage includes several species—Ochrosia borbonica, Tournefortia argentea, Hernandia peltata, Gyrocarpus Jacquinii—that are absent or extremely rare on the Malay Peninsula itself but widespread across the Indian Ocean and Malay Archipelago to the Pacific, suggesting a distinct insular littoral component (pp. 48–49).
The article also records several ecologically interesting observations: Ridley’s inference that Casuarina equisetifolia on these islands is dispersed primarily by sea currents rather than wind, based on the distance of seedlings from parent trees; the asexual propagation of a Daemonorops species by branch layering, which produces “reversed rattan” walking sticks that puzzle those unfamiliar with the mechanism; and the sighting of two killer whales (Orcas/Orcus gladiator) en route to Pulau Tengah, noted as a new mammal for peninsular waters (pp. 46–47).
Key Findings
- Fourteen new species were described from the expedition, including Polyalthia parviflora, Memecylon pulchellum, Webera adangensis, Webera insularis, Pinanga adangensis, Amorphophallus viridis, Schizostachyum insulare, Schizostachyum dumosum, Gymnostachyum insulare, Justicia inconspicua, Ophiorrhiza fontinalis, Phyllanthus (Reidia) glaucifolia, Peliosanthes parviflora, and Alsodeia hispida (pp. 49–64).
- Pulau Adang’s hill ridge reaches approximately 1,000 feet above sea level and is described as dry and barren at the summit, supporting only Curculigo latifolia, a few Pandans, and a Hornstedtia (p. 46).
- Cycas Rumphii attained a height of 20 feet on Pulau Butong and Pulau Rawi, representing a notable size for the species in the region (p. 62).
- Dracaena aurantiaca was observed in an exceptionally large form on Pulau Adang, approximately 50 feet tall and much branched, which Ridley had never previously seen at such a size (p. 46).
- Desmodium vestitum, previously known only from Malabar and Tenasserim, was collected on Pulau Butong, extending its known range (p. 52).
- The littoral flora of the Adang group includes Ochrosia borbonica, Tournefortia argentea, Hernandia peltata, and Gyrocarpus Jacquinii, all of which are absent or nearly so from the west coast of the Malay Peninsula despite suitable habitat, yet occur abundantly across the Indian Ocean and Malay Archipelago (pp. 48–49).
Conclusion
Ridley’s definitive takeaway is that the Pulau Adang group possesses a floristic identity that is distinctly Malayan in its woody forest component yet carries a strong insular-littoral signature linking it to the broader Indian Ocean–Malay Archipelago continuum rather than to the adjacent southern Siamese flora of the Lankawi islands. The islands thus represent a transitional zone where Malayan Peninsula elements and widespread oceanic littoral species co-occur in a configuration not replicated on the mainland coast.
Context
- Ridley was Director of the Singapore Botanic Gardens and one of the most prolific plant collectors and taxonomists working in the Straits Settlements and Malay Peninsula during the early twentieth century; this report follows the standard format of his field publications, combining narrative with a taxonomic checklist and new species descriptions.
- The expedition was facilitated by H. C. Robinson, who appears to have been a local collector or guide with prior knowledge of the islands (he had previously identified the sedge Remirea maritima for Ridley). The party’s composition—mixing botanical, zoological, and local collectors—reflects the collaborative, multi-disciplinary fieldwork typical of Straits Settlements scientific expeditions of the period.