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Thelocactus macdowellii (Rebut ex Quehl) C. Glass, Cact. Suc. Mex. 14: 4 (1969).
Basionym: Echinocactus macdowellii Rebut ex Quehl ('Mc. Dowellii'), Monatsschr. Kakt.-Kunde 4: 133-134 (1894).
Neotype: 33 km northeast of Saltillo on hy. 40 to Monterrey, Coahuila, Mexico, 22 July 1972, Edward F. Anderson 3182 (US 3047870).
Synonyms: Echinomastus macdowellii Br. & R., Cact. 3: 151 (1922). Neolloydia macdowellii H. E. Moore, Baileya 19: 166 (1975). Thelocactus conothelos var. macdowellii Glass & Foster ('mcdowellii'), Cact. Succ. J. (US) 49: 220 (1977). Thelocactus conothelos ssp. macdowellii var. sniceri Halda & Sladkovsky, Acta Mus. Richnov. Sect. natur. 7: 38 (2000).
Description
Stem single, globose, 4-10 cm tall, 4.5-12 cm wide. Ribs indistinct. Tubercles conical. Areoles without glands. Central spines 2-4, 10-50 mm long, white to greyish, straight, acicular. Radial spines 15-25, 8-20 mm long, white, straight, acicular. Flowers 40-80 mm wide, magenta.
Distribution
Mexico, Coahuila and Nuevo León, occurring in matorral xerofilo on limestone hills.
Comments
It is a rather common plant in collections, very much appreciated for its tight, dense and white spination. It is not so common in the wild, indeed only a few localities are known, between Saltillo and Monterrey. The stem is globose, completely divided into tubercles, with areoles bearing twenty or more white spines. The magenta flowers, of a lighter or darker hue, open between February and March. It may be confused with Thelocactus conothelos ssp. argenteus, from which it differs for the absence of areolar glands, the flower morphology and the micro-morphology of the seeds, which have convex testa cells and granular cuticle.
Thelocactus macdowellii
Ojo Caliente, Coahuila
Photo: A. Mosco
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Thelocactus macdowellii
Ojo Caliente, Coahuila
Photo: A. Mosco
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Thelocactus macdowellii
Ojo Caliente, Coahuila
Photo: A. Mosco
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Thelocactus macdowellii
CSD 192 Arteaga, Coahuila
Photo: A. Mosco
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home | © Alessandro Mosco 2004 | Last updated: 07-08-2005
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