An aroid collecting trip to Sarawak and a key to the genera of Araceae in Sarawak

The main aim of the trip was to find an enigmatic aroid that was first collected as a sterile plant by the Australian plant enthusiast Dr. A. Dearden in 1990. The true identity of this Nephthytis-like plant, as we called it in the meantime, remained unclear and we thought that it was probably a new genus. It was collected in flower shortly (6 February 1994) before our trip by Dr. A. Hay of the Royal Botanic Gardens, Sydney. We also collected this aroid in the rain forest and in relictual regrowth near Bintulu. It grows as scattered individuals on the forest floor. Living plants brought back to Germany and England have grown very slowly, although one plant has flowered in the Botanischer Garten München. A thorough study of this aroid, including fruiting material, pollen morphology and chromosome count has shown it to be a new species of Nephthytis, a genus hitherto known only from the rain forest areas of tropical Africa. This is the first record of the genus Nephthytis in Asia. A similar disjunction of distribution occurs in the genera Amorphophallus, Arisaema, Remusatia, Rhaphidophora, Sauromatum, and Pothos (the last one in Madagascar and the Comores, not on the African mainland). However these occur in the Indian subcontinent as well. Nephthytis does not. The new Asian species has been described as Nephthytis bintuluensis by Hay, Bogner & Boyce (1994). Another interesting observation made during our trip was that Pedicellarum paiei M. Hotta (the only aroid with pedicellate flowers) has four growth stages: a monopodial juvenile ‘shingle plant’ with nearly sessile ovate to round leaves appressed to the trunk of the climbing support, a monopodial sterile semi-mature stage with differently shaped, petiolate leaves, a fertile sympodial stage with the inflorescences carried on numerous abbreviated side branches and a flagellate stage, with long whip-like growths bearing scale-like leaves, arising from the sympodial flowering stage. The flagellate shoots reach a length of several metres and continue to grow until they reach the ground or another tree at which point they produce roots and resume the second growth pattern described above.