Local name Belian or Belian simpoh. The wood is known as Ulin. Note that there are two different trees called Belian in Borneo. Potoxylon melangangai is most common on the west coast of Borneo and Eusideroxylon zwageri which is most common on the east coast of Borneo. Both tree species have very hard, very heavy wood and are most common on river floodplains often in single species stands. The seeds of both species are often found on beaches near river mouths and can be told apart as described below.
All the seeds shown below were found under one of the two Belian trees which grow next to the Ulu Ulu Resort in Temburong, Brunei. One tree grows next to the swampy stream which runs under the walkway leading to the guest cabins along the river. The other tree grows near the steps leading down to the boat jetty and overlooking the second stream which runs under the forestry building, in a concrete channel.
Note that the longitudinal grooves on this Belian seed are only superficial and are filled with a corky substance. The seeds of Eusideroxylon zwageri have deep longitudinal corrugations.
The grooved seed is covered in a thin layer of flesh which is difficult to clean off the bare seed as illustrated below. Once the thin green skin is removed, the flesh is extremely slimy and slippery so it is almost impossible to hold the seed in the hand. One can imagine a rhino taking a seed in its jaw to try and scrape off the flesh and the seed is so slippery that it is almost inevitably swallowed by the rhino which actually gains no benefit from swallowing the large hard seed..
