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Angraecum sororium Schltr., Repert. Spec. Nov. Regni Veg. Beih. 33: 360 (1925).
Homotypic Synonyms:
Macroplectrum sororium (Schltr.) Szlach., Mytnik & Grochocka, Biodivers. Res. Conservation 29: 18 (2013).
Description:
Plants stiff, to 60 cm tall, nearly always simple, very compressed (10-l5 mm. wide), bearing numerous cases in the upper quarter. Leaves distichous, rigid, lingulate (18-30 x 3-4.5 cm.), unequally bilobed rounded apically. Inflorescence shorter than the leaves, 1-3 per stem, 1-4 flowered; bracts obtuse, 3 cm long. Carinate-winged dorsally, flowers of a glowing white, large (divisions 5-6 cm long). Sepals much wider 16 mm) basally, attenuate from the base to the acute apex, provided with a dorsal keel, the laterals with the keel more projecting and joined basally between their bases and front margins, forming a wide gutter at the bottom of which the spur oriface if located. Petals of the same length and form, but wider (2 cm) and provided with a small auricle basally on us internal margin. Labellum longer than the petals, sub orbicular (30-33 mm wide) below the terminal acumin, which is thick-conical and acute; provided basally with 2 large, humpshaped, thick calluses; spur 25-32 cm long, pendent, cylindrical, 4-5 mm in diameter at the oriface, then gradually attenuate to the l mm apex. Column 7 mm tall, thicker than tall; clinandrium small by comparison with the wider column, back margins not projecting; auricles subsquare (5 x 5 mm) inferior angle straight, the superior obtuse and more projecting: with a narrow and acute median tooth of the rostellum (0.5 mm tall), in the notch. Anther very depressed, 5 mm wide, widely notched in front with the terminal edges tipped with an acute tooth; pollina white, obpiriform (3 x 2 mm), on a common retinacle, very widely rhomboid-oval (4 x 4 mm), notched or bifid apically. and slightly pleated-saddle shaped. Pedicel 4-6.5 cm long.
Habitat:
This terrestrial or lithophytic orchid is found in the central highlands in the region around Antananarivo as well as several other locations where it grows almost fully exposed on among boulders and granite outcrops at 5250-7200 ft. (1600-2200 m). Hillerman & Holst (1986) report that in the habitat these plants experience frequent but brief frosts and early-morning freezes during the winter months. Mists and heavy dews are common during the remainder of the year. Flowering: January-March.
Cultivation:
Read more of Cultivation of Angraecum sororium Schltr.
Notes:
Angraecum sororium is a fairly large, but slow-growing, stately handsome plant that is absolutely breath-taking when in its full floral glory. Old plants produce many (a dozen or more) keikis from their base and thus form clumps. The flowers of this species are similar to those of Angraecum magdalenae, though considerably larger, and they generally conform to the present-day concept of the perfect orchid flower, in terms of flatness, roundness, and lack of space between flora segments. The flowers are pure white with green spur, are of heavy substance, and have moderately good lasting qualities.
Distribution:
Madagascar
References:
De la Bathie, H., and H. Humbert. [1939, 1941] 1981. Flora of Madagascar 1-2. The Government of Madagascar and the National Museum of Natural History, Paris. Translated and published in 1 vol., Steven D. Beckman, 621 Palm Ave., Lodi, CA, U.S.A. 95240. Du Puy, D., P. Cribb, J. Bosser, and J. and C. Hermans. 1999. The Orchids of Madagascar. The Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, England. Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211 Beckwith Road, Richmond, B. C., Canada V6X 1V7. Hillerman, F. and A. Holst. 1986. An introduction to the cultivated Angraecoid orchids of Madagascar. Timber Press, Portland, Ore. Kew Data Base. 2014. http.//apps.kew.org/wcsp/home.do Stewart, J., J. Hermans, and B. Campbell. 2006, Angraecoid Orchids. Timber Press, Portland, OR.; WCSP (2017). 'World Checklist of Selected Plant Families. 24.01-2017; http://apps.kew.org/wcsp/
Images:
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In culture	In culture	In culture	In culture
Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.

Habitat/ In situ	Habitat/ In situ	Habitat/ In situ	Habitat/ In situ	Habitat/ In situ	Habitat/ In situ
Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.	Photograph Gilles Grunenwald. Image used with kind permission.