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Angraecum section Hadrangis Schltr., Beih. Bot. Centralbl. 36(2): 158 (1918).
Description:
Epiphytic on canopy or trunk, large plants (to 35 cm height); stems erect, short or elongate, internodes short; leaves dense, coriaceous; inflorescences racemose, few to severalflowered (up to 10), suprafoliar, short or equaling leaves, one to four per stem; flowers medium, white, sepals and petals lanceolate-ovate; labellum lowermost, ovate, deeply concave, shorter or equaling dorsal sepal, white overlaid green at the moth, apex acute; spur shorter than dorsal sepal, conic or saccate, with a wide opening, green; ovary round in section with 180° resupination.
Notes:
Species of section Hadrangis can be readily separated by the aperture pattern of the flower, or in other words, by the area available for an animal to access the nectar. This was determined by measuring the distance between the labellum to the base of the pollinia, and the distance between the edges of the labellum. These two-dimensional measurements show a unique flower aperture pattern for each species. Angraecum cadetii has the largest aperture ratio (for both 'height' and 'width') of the four species, allowing small birds (Zosterops spp.) to reach its nectar but without removing the pollinia. Flowers of the other three species have smaller aperture ratios. This smaller aperture of the flower forces Zosterops spp. to be in contact with the orchid column when probing for nectar, resulting in the bird effecting pollination, since pollinia end up sticking to their beaks. Pollination by Zosterops was observed for both A. bracteosum and A. striatum in Réunion (Micheneau et al. 2006, 2008b). As A. jeannineanum has an aperture ratio in-between of these two species, it is expected that it is probably pollinated by a Zosterops, but this has not been observed yet.
This is one of the few sections clearly typified by Schlechter. The sectional name Thouarsiangraecum is superfluous because it was also typified by Angraecum striatum Thou. The poorly known A. coriaceum (Sw.) Schltr. is closely related to A. bracteosum Balf. f. & S. Moore. Inflorescence racemose, several-flowered. Flowers fleshy. Ovary commonly short pedicellate. Spur short, conical or saccate, obtuse with a wide opening. Stems rather short or hardly developed.
Type:
Angraecum striatum Thou.
Species:

World Checklist of Monocotyledons.The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; http://www.kew.org/wcsp/monocots/ accessed 13/02/2017