Mystacidium Lindl., Companion Bot. Mag. 2: 205 (1837).
Description:
Plants epiphytic, monopodial without pseudo-bulbs; stems very short; roots simple, clustered at the base of the leaves; leaves distichous, sheaths imbricate, blades lorate, conduplicate at the base and flat apically, unequally bilobed, disarticulating from the persistent sheaths. lnflorescences of several lateral, spreading or pendent racemes, borne below the leaves; peduncles with several small sheaths; bracts mostly tubular, papery, very small. Flowers small, white or pale green, resupinate. Se-pals subequal; median lorate; laterals more or less rhomboid. Petals smaller than sepals. Lip ecallose, 3-lobed; midlobe sharply deflexed, acute; side lobes small, flanking the entrance to the spur; spur long, tapering from a wide, bell-shaped entrance to an acute apex, often curved. Gynostemium erect; pollinia 2, stipes and viscidia separate; stigma forming a very deep cavity below the rostellum; rostellum more or less equally 3-lobed.
Type species:
Mystacidium capense (L. f.) Schltr.
Habitat:
The genus Mystacidium is adapted to a wide spectrum of elevations. It occurs from sea level (M. aliceae) to 2,000 meters (M. gracile). Most of the species are found inland at elevations of 900 - 1,200 meters. Some species prefer to grow in deep shade (M. aliceae) but most of them prefer light shaded conditions. Only two species (M. capense andM. venosum) thrive in full sunlight and occur naturally in Acacia (thorn tree) woodland.
These lowland woodlands experience a long and dry winter period) with the Mystacidium plants surviving on food stored in their thick and leathery leaves. Air humidity during this period is extremely low with the roots merely anchoring the plant to the phorophyte. The leaves of these two species are usually strongly V-shaped to channel the slightest amount of moisture to the stem and roots. M. aliceae occurs in thick scrub forest on hill slopes along river valleys. This is one of the species that does not require copious airflow. In it's natural habitat there are long periods with little to no movement of air, only experiencing build-up of high humidity every now and then. The result is usually a light down- pour lasting less than an hour.
Most species prefer to grow on the edges (ecotone) of cool evergreen montane forests where they receive morning mists and lots of airflow. The ecotone or forest margin is usually that part of the forest with the highest species diversity (fauna and flora). Mystacidium plants that grow in the forest usually develop many roots and grow on thick branches and trunks in the upper canopy where they receive sufficient airflow.
The plants growing on the forest margin usually have fewer roots and grow on thin branches. They do not need many roots to absorb the available moisture as the mist is blown on to them and in this way they receive more than enough moisture.
Notes:
The genus Mystacidium (from the Greek mystax meaning moustache) was described by John Lindley during 1836 in William Hooker's Companion to the Botanical Magazine (Hooker, 1836). Mystacidium is closely allied to the genera Aerangis from Africa, Madagascar and Sri Lanka (Stewart, 1979) and Angraecopsis from Africa and Madagascar (Williamson, 1977; Ball, 1978) but differs in the papillate to bearded or hairy 3-lobed rostellum and also in the structure of the pollinarium. Most Mystacidium species are superficially similar and sometimes difficult to identify. The shape and size of the lip are the best characters to separate the species. Some of the species are threatened by the destruction of their forest habitat, over- collecting by individuals and the illegal export of the material.
The taxonomy of this genus is unsatisfactory.
Here much emphasis has been placed on the flowering times, but the taxa so produced are not clearly separated by morphological characters. Classification is also bedevilled by the small size of the flowers, and the generally inadequate collections of liquid-preserved material.
Cultivation:
All species of Mystacidium are easily grown. The easiest method is to mount the plant on large pieces of bark or on slabs of tree fem stem. Mystacidium plants never seem to thrive if planted in pots, irrespective of the growth medium used. They need a good flow of air over their roots. As soon as the inflorescences appear, they need high humidity conditions. It is not necessary to keep the plants under a mist spray, they are equally happy if you water them with an ordinary spray nozzle. It appears as if Mystacidium plants grow the best under light shaded conditions out of their natural habitat. M. capense and M. venosum will grow equally well and flower if keep in full sun.
Distribution:
Tanzania to S. Africa
Species:

Bibliography and References:
Carlsward BS, Stern WL, Bytebier B. 2006 Comparative vegetative anatomy and systematics of the angraecoids (Vandeae, Orchidaceae) with an emphasis on the leafless habit. Bot. J. Linn. Soc. 151. 165-218;. Duckworth A. 1979 Mystacidiums in South Africa. S. Afr. Orchid J. 10. (2): 48 - 49 (1979); Gasson P, Cribb PJ. 1986 the leaf anatomy of Ossiculum aurantiacum Cribb & van der Laan (Orchidaceae: Vandoideae). Kew Bull. 41. 827-32; McDonald GJ. 2007 The genus Mystacidium Lindl. Orchids S. Afr. 38. (1): 6-13; Northen RT. 1981 Mystacidium millarii: an exciting South African species. Amer. Orchid Soc. Bull. 50. (2): 173 - 175 (1981); Pottinger M. 1979 The mighty miniatures: five African beauties. Orchid Rev. 87. (1031): 170 - 173 (1979); Pottinger M. 1982 African orchids: genera from 'G" to 'M'. Orchid Rev. 90. (1068): 327-329 (1982); Venter F. 1999 Notes on the identification of the genus Mystacidium Lindl. in South Africa. Austral. Orchid Rev. 64. (5): 22-27 (1999); Venter HJ. 1995 Mighty miniatures: no.11. Mystacidium venosum. S. Afr. Orchid J. 26. (4): 146 (1995); WCSP (2017). 'World Checklist of Selected Plant Families. 07.03-2017; http://apps.kew.org/wcsp/