Oxysepala

Bulbophyllum is a genus of mostly epiphytic and lithophytic orchids in the family Orchidaceae. It is the largest genus in the orchid family and one of the largest genera of flowering plants with more than 2,000 species, exceeded in number only by Astragalus. These orchids are found in diverse habitats throughout most of the warmer parts of the world including Africa, southern Asia, Latin America, the West Indies, and various islands in the Indian and Pacific Oceans. Orchids in this genus have thread-like or fibrous roots that creep over the surface of trees or rocks or hang from branches. The stem is divided into a rhizome and a pseudobulb, a feature that distinguished this genus from Dendrobium. There is usually only a single leaf at the top of the pseudobulb and from one to a large number of flowers are arranged along an unbranched flowering stem that arises from the base of the pseudobulb. Several attempts have been made to separate Bulbophyllum into smaller genera, but most have not been accepted by the World Checklist of Selected Plant Families. Plants in the genus Bulbophyllum are epiphytic or lithophytic sympodial herbs with thread-like or fibrous roots that creep over the surface on which they grow. The stem consists of a rhizome and a pseudobulb, the latter with one or two usually fleshy or leathery leaves. The flowers are arranged on an unbranched raceme that emerges from the pseudobulb, usually from its base. The dorsal sepal is free from the lateral sepals which themselves may be free or fused to each other. The petals are also free from each other and smaller than the lateral sepals. The labellum is often fleshy, curved and hinged to the base of the column. The genus Bulbophyllum was first formally described in 1822 by Louis-Marie Aubert du Petit-Thouars in his book Histoire particulière des plantes orchidées recueillies sur les trois Iles Australes d’Afrique, de France, de Bourbon et de Madagascar in which he described eighteen species of Bulbophyllum. There are now more than 2,800 records (accepted names and synonyms) for this genus. This large number and the great variety of its forms make the genus a considerable challenge for taxonomists: 120 sections and subgenera have been listed. The genus name (Bulbophyllum) is derived from the Greek bolbos meaning 'bulb' and phyllon, 'a leaf', referring to the pseudobulbs on top of which the leaf grows. The center of diversity of this genus is in the montane forests of Papua New Guinea (more than 600 species) which seems to be the evolutionary homeland, though the genus is pantropical and widespread, occurring in Australia, Southeast Asia (with over 200 species in Borneo), India, Madagascar (with 135 species, some endemic), Africa and in tropical central and South America. The erect to pendent inflorescence arises laterally from the base of the pseudobulb. The flower form has a basic structural blueprint that serves to identify this genus. But this form can be very diverse : compound or single, with few to many flowers, with the resupinate flowers arranged spirally or in two vertical ranks. The sepals and the petals can also be very varied : straight or turned down, without footstalk or with a long claw at the base. They are often hairy or callous. There are two to four hard and waxy pollinia with stipes present or absent. The fruits are beakless capsules. Many Bulbophyllum species have the typical odor of rotting carcasses, and the flies they attract assist in their reproduction through pollination. Nevertheless, some species with mild and pleasant floral fragrance attract Dacini fruit flies (particularly Bactrocera and Zeugodacus species) via methyl eugenol, raspberry ketone or zingerone that also act as floral reward during pollination.