AFRICAN

ORCHIDS

Aerangis Rchb.f., Flora 48: 190 (1865).
Synonyms:
Radinocion Ridl., Bol. Soc. Brot. 5: 200 (1887).
Barombia Schltr., Orchideen: 600 (1914).
× Barangis auct., Orchid Rev. 90(1065) cppo: 8 (1982).

The genus Aerangis was established by H. G. Reichenbach in 1865 for species that had a long, slender rostellum and a lip that did not envelop the Column at the base, but otherwise resembled Angraecum. The name is derived from the Greek words aer (air) and angis (vessel), presumably in reference to the long, hollow spurs. The type species was Aerangis flabellifolia from Angola, a name that is now considered a synonym of A. brachycarpa. Several species now placed in Aerangis were known before 1865, but had been put in other genera, usually Angraecum. The first species known, the West African Aerangis biloba, was described as Angraecum bilobum.
Description:
Epiphytic herbs with short or elongated woody stems bearing numerous elongated aerial roots in the lower part. Stems usually unbranched, covered with the remains of overlapping leaf bases, bearing few to several leaves apically. Leaves in 2 rows, usually thick and fleshy in the living state, sometimes leathery during the dry season, sheathing at the base, much longer than broad and usually wider in the upper half, unequally bilobed at the apex. Inflorescence lateral, a short or elongated raceme, rarely branched, few- to many-flowered. Flowers resupinate, white or variously tinted with green or brown. Sepals and petals free, spreading or reflexed. Lip entire, often similar to the sepals and petals, spurred at the base. Column short and stout or somewhat elongated and more slender, often narrowed towards the base and enlarged at the level of the stigma; androclinium straight or sloping, the anther cap sometimes beaked; rostellum entire, elongated, deflexed or porrect; pollinia 2, sessile on a single stipes; viscidium variously shaped; stigma an oval or rhomboid sticky depression. Ovary elongated, straight or curved. Capsule cylindric or ellipsoid, often much elongated.
Notes:
A distinctive feature of the entire genus is the rostellum on the front of the more or less elongated column. It projects forward or downward from the base of the androclinium across the surface of the stigma. In Aerangis fastuosa it is so long that its tip is hidden in the spur, while in A. monantha and A. punctata it is quite straight and extends below the column across the mouth of the spur. In other species it curves forwards so that the viscidium itself is held in a horizontal position in front of the stigma.
Distribution:
The genus is widespread in tropical Africa and Madagascar, although some species are very restricted in their distribution, and for many species the plants are not common even where suitable habitats exist. Thirty-one species are now recognised from continental Africa. Twenty-one are recorded from Madagascar, 5 of which are also found in the Comoro Islands and one in Réunion. One species has been recorded from several places along the coast of East Africa and in Sri Lanka.
Culture:
Specimens of this genus are amongst the most attractive and highly sought-after of the white-flowered epiphytes of Africa and Madagascar. The plants vary in size and shape but most have dark green or greyish-green leaves on upright or pendent stems. The flowers are graceful, white or cream, and sometimes tinged with green or pinkish brown. Two small-flowered species in Madagascar are pale green or brownish green. There may be many flowers on each raceme, or only one or few, and often there are several inflorescences on each plant at one flowering. The flowers may appear at any time of the year but in the wild they are most common during the rainy seasons in April and May or October and November in Africa and in January and February in Madagascar and neighbouring islands.
All the species are easily maintained in cultivation. The species from higher altitudes need cooler conditions than those that occur at or near the coast. They all grow well mounted on a piece of bark or timber that is suspended in deep shade, usually in high humidity. Well-rooted plants will also do well in pots in any compost that is suitable for epiphytic plants. The hardest thing to arrange, in cultivation, is the resting season that most species enjoy after flowering and fruiting. If plants are kept dry, they will dry out too much and lose their leaves. Conversely, if they are sprayed too much, the roots and leaves will suffer from overwatering and the plants will die. Careful management of the plants and their environment will ensure that they are long-lived and flower prolifically.
Species from Africa
The Africa species are arranged here in 4 groups according to the size of the flowers, in particular the length of the spur:
Aerangis Group 1.
Flowers with a spur 10 cm long or more.
Aerangis Group 2.
Flowers with a spur 4—9 cm long.
Aerangis Group 3.
Plants small, flowers with a narrow lip and a spur less than 4 cm long.
Aerangis Group 4.
Plants small, flowers with an obovate or suborbicular lip, widest towards the apex.
Aerangis Species from Madagascar and Comoro Islands:
Many of these species were introduced into cultivation in the nineteenth century and at that time, and later, names were misapplied to several well known species. In sorting out the taxonomy and nomenclature of these popular plants we have had a few surprises. In the account that follows, the names are used in the same way as in another recent publication (Hermans et al., 2006), and we have included here some of the most well known synonyms which have been and still are being used in horticulture.
All the species occur in Madagascar, 6 have also been found in the Comoro Islands and one, Aerangis punctata, has been discovered recently in Réunion. They have presented them here in 5 groups to facilitate identification:
Aerangis Group 1.
Plants medium-sized or large, flowers many, white or tinged pale pink, with a long spur at the base of the lip, open and star shaped with broad tepals and lip.
Aerangis Group 2.
Plants sometimes rather large, some with greyish-green, succulent leaves; flowers with sepals and petals, and sometimes the 1, strongly reflexed so that the flowers appear flattened; lip with a long spur.
Aerangis Group 3.
Plants rather small, leaves dark green, inflorescences with many small white or whitish flowers.
Aerangis Group 4
Plants rather small, with 2-6 small leaves and few large white, yellow and white, or pink-tinged flowers with a broad mouth to the spur. Three of the species are noteworthy for the long rostellum which extends downwards across the face of the stigma.
Aerangis Group 5.
Plants rather small, with many small pale green or yellowish green flowers.
These groups are not intended to indicate relationships; they are used here as an aid to identification.
Aerangis species some not yet are in location.
Bibliography and References:
Anon. 1998 Two new Aerangis species. Correction to figs 127-128, pages 226-227 July/August issue. Orchid Rev. 106. (1223): 299 (1998)
Arends JC, Stewart J. 1989 Aerangis gracillima: a definitive account of a rare African orchid of Cameroun and Gabon. Lindleyana 4. (1): 23-29 (1989)
Bellone R, Chiron G. 2002 Aerangis xchirioana, un hybride naturel du Cameroun. Richardiana 2.
Cavestro W. 1998 Aerangis distincta J. Stewart et I.F. La Croix. Orchidophile 29. (134): 219-223 (1998)
Chiron G, la Croix I, Stewart J. 1998 Two new species of Aerangis from tropical Africa. Orchid Rev. 106. (1222): 225-230 (1998)
Cribb PJ, Herrmann C, Demissew Sebsebe. 2002 New records of orchids from Ethiopia. Lindleyana 17. (1): 178-188 (2002)
Fibeck W, Dare M. 1997 Aerangis rusituensis: a new species from eastern Zimbabwe. S. Afr. Orchid J. 28. (3): 73-76 (1997)
Hermans J. 2002 Plant portrait 449. Aerangis ellisii var. grandiflora. Orchidaceae. Curtis's Bot. Mag. 19. (3): 178-183 (2002)
Herndon CN. 1997 Colorful Angraecoids Amer. Orchid Soc. Bull. Aug., 816-823.
Knight G. 1994 Aerangis punctata (J. Stewart). Orchids Austral. 6. (6): 59 (1994)
La Croix I. 1994 Plant portraits: 242. Aerangis arachnopus. Orchidaceae. Kew Mag. 11. (2): 55-59 (1994)
La Croix I. 1994 The angraecoid orchids: 4. Aerangis. Orchid Rev. 102. (1196): 91-96 (1994)
La Croix I. 1996 Plant portrait: 300. Aerangis distincta. Orchidaceae. Curtis's Bot. Mag. 13. (3): 146-152 (1996)
La Croix I. 1998 Plant portraits: 333. Aerangis verdickii. Orchidaceae. Curtis's Bot. Mag. 15. (1): 20-26 (1998)
La Croix I. 1998 Whatever happened to Barombia? Orchid Rev. 106. (1223): 291-293 (1998)
La Croix IF. 1989 Aerangis in Malawi. Orchid Rev. 97. (1153): 343-349 (1989)
Leroux, A. (1975) Aerangis rhodosticta. L'Orchidophile, 20, 485.
Leroux, A. (1977) Aerangis biloba. L'Orchidophile, 28 791.
Leroux, A. (1989) Aerangis collum-cygnii & A. kotschyana. L'Orchidophile, 88, 182.
Leroux, A. (1989) Aerangis gravenreuthii = A. stella. L'Orchidophile, 85, 22.
Leroux, A. (1989) Aerangis megaphylla Summerh. (Aerangis phalaenopsis). L'Orchidophile, 85, 12.
McDonald G. 2006 The genus Aerangis in South Africa. Orchids S. Afr. 37. 35-38.
Stewart J, La Croix I. 1987 Notes on the orchids of southern tropical Africa III; Aerangis. Kew Bull.
Stewart J, La Croix, IF. 1987 Notes on the orchids of southern tropical Africa: 3. Aerangis. Kew Bull. 42. (1): 215-219 (1987)
Stewart J. 1986 Stars of the Islands: a new look at the genus Aerangis in Madagascar and the Comoro Islands: 1. Amer. Orchid Soc. Bull., 55. (8): 792-802 (1986)
Stewart J. 1986 Stars of the islands: a new look at the genus Aerangis in Madagascar and the Comoro Islands: 2. Amer. Orchid Soc. Bull., 55. (9): 903-909 (1986)
Stewart J. 1986 Stars of the islands: a new look at the genus Aerangis in Madagascar and the Comoro Islands: 3. Amer. Orchid Soc. Bull., 55. (10): 1008-1015 (1986)
Stewart J. 1986 Stars of the islands: a new look at the genus Aerangis in Madagascar and the Comoro Islands: 4. Amer. Orchid Soc. Bull., 55. (11): 1117-1125 (1986)
Stewart J. 1987 Aerangis spiculata Kew Mag 4. 69-74.
Stewart J. 1987 Plant portraits: 77. Aerangis spiculata. Kew Mag. 4. (2): 69-74 (1987)
Stewart J. 1988 Fine species at Westminster: Aerangis hyaloides. Orchid Rev. 96. 16-17.
Stewart, J. (1979) A revision of the African species of Aerangis (Orchidaceae). Kew