The Genus Aporum
In the 1990s, when the senior author was still living in the Philippines, he was out in the forest one day, with a local guy acting as his guide. Whenever we found a fallen tree, we would look it over and rescue any orchids that were still alive.
Bear in mind that my guide had no interest in orchids, or plants in general (unless they were edible).
Upon returning to the house we started to sort the plants into their different genera. The bulbophyllums were readily distinguished because of their growth habit, as were the vandaceous species. When we got to the dendrobiums an interesting thing happened. There were about a dozen plants of Dendrobiinae and my friend divided them into several groups, because of the growth habit of the plants. He separated the Aporum species, the plants of Dendrobium crumenatum and Dendrobium philippinense, and a plant of Dendrobium anosmum made a third group. When I told him that all three separate groups were one genus he looked at me and said “Well the plants all look different to me.”
In 1825, Dr. Carl Blume established the genus Aporum based on a plant he named Aporum lobatum. A few years later Dr. John Lindley proposed that Aporum was better defined as a section of the large genus Dendrobium. This proposal was followed by most botanists and taxonomists for many years; until 1981, when Brieger and Rauschert made some rather revolutionary (at the time) taxonomic transfers.
This group of plants remained in the genus Dendrobium until recent studies by Dr. Mark Clements, from the Australian National Herbarium, in Canberra. These studies, which are backed up with DNA findings, prove conclusively that Aporum is a distinct genus, readily separable from Dendrobium.
Is it possible that too much emphasis is placed on floral characters, when vast differences in plant habit are as plain as the nose on one’s face?
Plants from the genus Aporum have equitant leaves which are hard and fleshy, broadest at the base of the leaf and then tapering towards the apex. There are no readily discernable pseudobulbs in this genus. The usually small flowers are produced singly.
In some species, the flowering portion of the plant is a leafless extension to the leafy stem. In other species, the flowers appear from a group of bracts at the apex of the leaves. Most of the species are uncommon in cultivation and are usually only seen in specialist collections. Even though the flowers are, in most species, small, the plants are an interesting addition to any orchid collection. Aporum aloifolium is a widelydistributed species which has been recorded from Thailand, Peninsular Malaysia, Indonesia, Borneo and the Philippines. It grows at low elevations and in some localities, it becomes very common. The sepals and the petals reflex prominently and the diameter of the bloom is barely 3 millimetres.
Aporum distichum appears to be endemic to the Philippines where it is
widely spread. It grows at elevations up to 1,400 metres. Flowers are about 6 mm in diameter. There is also a form of this species, which lacks the red striping on the floral segments.
Aporum merrillii is another Philippines endemic and has been found on the large island of Luzon, Samar and Mindoro just south of Luzon. It grows at low elevations in sunny locations. Flowers are about 4 mm in diameter.
Aporum wenzelii only occurs in the Philippines and has been recorded from all the major islands. It is also a species from mid-elevations and has not been recorded below 400 metres. The bright orange bracts, from which the flowers emerge, are an attractive feature of this plant. The flowers are about 7 mm in diameter. A small growing plant.