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BULBOPHYLLUM

Category: Plants and Orchids
Date Posted: 2006-10-11

AS THE ORCHID FAMILY IS ONE OF THE LARGEST OF THE major subdivisions of flowering plants, so is the genus Bulbophyllum the largest group of closely related plants within the family Orchidaceae. This extensive genus includes more than twelve hundred species which are distributed over a tremendous area from Africa through Tropical Asia-Malaysia, extending to portions of Oceania, including Australia, New Guinea and New Zealand.

In systematic botany, the genus Bulbophyllum is arranged close to the genera Dendrobium and Eria to which it is allied, differing primarily in the form of the inflorescence. The genus is also associated geographically with the Dendrobium and Eria and frequently throughout the Philippines, plants of all three groups can be collected from the same host tree.

This genus was established by Thouars in 1822 upon plants collected from Africa, and the generic name means a bulblike leaf. The genus is characterized by a sympodial growth, and after a pseudo-bulb and accompanying leaves have been produced, growth of that particular bulb does not continue; instead a creeping rhizome and a new pseudobulb with accompanying leaf is produced. Besides being the largest of the orchid genera, this group has the added distinction that its flowers are considered to be among the most remarkable of those of a family already recognized for its bizarre and unusual inflorescence. The genus is characterized by a peculiar, fleshy, highly colored labellum which is articulate (hinged) at its base and trembles or bobs up and down at the slightest movement of the plant or flowers. Insects of suitable size, upon alighting on this strangely modified organ and crawling beyond its point of balance, are thrown forward by the motion of the labellum, so that they are head downward with their thorax on the inner surface of the column.

In struggling to regain their freedom they remove the pollen, only to leave it on the stigma of the next flower visited. This arrangement which is a marvelous adaptation of the reproductive organs of the plant is quite conspicuous in the flower of B. Dearei, a species which has thickened roundish pseudobulbs about one inch long and a single leaf, approximately six inches long. The single flower, which tops a six-inch flower stem, is about 11/2 inches across. This plant can be collected from the medium altitude forests on Luzon and other islands. It was originally described in 1883 and is probably dedicated to Lt.-Col. Deare, of Englefield Green, near Engham, England, who apparently first flowered it. The plant is a member of the sub-genus SESTOCHILUS.

In most Bulbophyllum flowers, the petals are small in size, often inconspicuous and sometimes with antenna-like threads terminated by small balls. The sepals usually make up the larger portion of the flower. Some members of this genus differ greatly from those which are considered the typical species and consequently various authorities have found it advantageous to divide the group into a number of subgenera. In fact in the past, it was the opinion that certain groups were so distinctive as to warrant their being classed as separate genera. This tendency has resulted in some confusion regarding correct nomenclature and the principal group so affected is that which is often designated as cIRRxoYETALUm. This is a group of plants distinguished by the more or less "umbel"-like arrangement of the inflorescence. Also the lower sepals of the flowers, which are greatly elongated. are united (connate) the greater part of their length and twisted so that the lower surfaces are uppermost. This twisting develops at the base and allows ample room for the bobbing movement of the labellum. The upper sepal and petals are often adorned with "hairs."

Dr. Lindley established the section CIRRHOPETALUM as a genus in 1824 upon C. Thournasii, an African species. He separated the group from the Bulbophyllums because th. type of species was quite different from all of the other Bulbophyllums known at that tilne. Some years later when additional material became available, Reichenba