ARACHNIS | Herbarium Digital Library


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ARACHNIS

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

THE GENUS ARACHNIS COMPRISES A GROUP OF ABOUT FIFTEEN to twenty unusual and interesting plants, which are dispersed throughout the Indo-China-Malaysian area, extending to the Philippines. The genus is closely allied to the Vanda, Vandopsis and Renanthera and includes one of the most unusual of all orchids, A. Lowii (Vanda Lowii), from Borneo. This genus differs from the Vanda in the form of its perianth segments, especially the labellum which is neither saccate nor spurred as it is in the Vanda. The' distinguishing feature of the Arachnis is that the lip is joined to the base of the column by a short, thin flexible portion which forms a hinge so that the lip moves freely without injury. The genus Renanthera is characterized by a lip that is joined to the base of the column by a thin portion, so that the lip is slightly movable; but there is no special hinge as in Arachnis. The lip of the genus Vandopsis is firmly united to the base of the column by a rather small side lobe.*

The genus Arachnis was established by Blume on the species A. Flo.r-aerir which has wide distribution through the Malaysian area and is reportedly found in the southern islands of the Philippine Group. He later re-designated the genus and called it Arachnanthe, a name which remained in use until the end of the past century. At that time, however, it was reinstated as Arachnis because of the rule of prior usage.

A.Flos-aeris was originally described as Epidendrum Flosaeris by Linnaeus and still later designated Arachnis morchitera as the typical species of the genus Arachnis. Because of the rule of prior usage, the name was changed to A. Flos-aeris. The generic name Arachnis (Arachnanthe) refers to the spider like appearance of the flower of the typical species.

This species is a ground orchid similar in habit and growth to Renanthera Storiei. The plant often grows to a height of eight to ten feet and has leaves 1 1/2 inches wide, about four to six inches long, that are acuminate or pointed. Like R. Storiei, this Arachnis is a climbing plant that develops rather large roots for support. The flower stalk arises from the upper nodes of the stem and often exceeds a foot in length. The raceme consists of about ten flowers, each 'of which is almost three to four inches across, yellowish-white and spotted and cross-barred with blotches of purple brown. This spider-like flower is unusual in that it emits a strong scent of musk from the upper end of the dorsal sepal. This peculiar flower lasts for more than a month in perfection and flowers for a considerable portion of the year from July to March. The cultural requirements of this plant are similar to those required by Renantheras and it should be grown in almost full sunlight. The specific name Flos-aeris means "Flower of the Air."