One of the least understood of the Mexican cacti is Ortegocactus, known only from Oaxaca. Tom MacDougall discovered the plant in the winter of 1951-1952 near the village of San José Lachiguiri and sent specimens to Edward Alexander at the New York Botanical Garden. After the plants flowered and produced seeds, Alexander concluded that though the cactus is similar to Coryphantha and Mammillaria, it is distinct enough to be placed in its own genus, which he named Ortegocactus (type, O. macdougallii), honoring the Ortega family of San José Lachiguiri, who had aided MacDougall in discovering the plant.

Botanists have puzzled over the species and where to place it in the classification of cacti. In 1974 Leo Kladiwa made Ortegocactus a subgenus of Neobesseya, which Helia Bravo-Hol-lis and Hernándo Sánchez-Mejorada ( 1991,2:395) accepted. However, Alan Zimmerman (1985) considered Ortegocactus to be basal to his Coryphantha line, including Escobaría and

Neobesseya, and believed it distinct from either Ferocactus or Mammillaria. Further research is necessary, especially DNA sequencing, to determine if Ortegocactus should be included in another genus; it seems appropriate at this time to consider it a separate genus of a single species.

Ortegocactus Alexander 1961 Neobesseya subg. Ortegocactus (Alexander) Kladiwa 1974 Subfamily Cactoideae, tribe Cacteae.

Ortegocactus macdougallii Alexander 1961 Neobesseya macdougallii (Alexander) Kladiwa 1974

Plants usually caespitose, forming loose clusters of many low-growing stems. Stems globose to short cylindrical, pale gray-green, 3-4 cm (1.2-1.6 in) in diameter. Tubercles low, spirally arranged, somewhat flattened, rhomboid, minutely dotted. Areoles dimorphic, bearing wool and spines in the upper part, sometimes with grooves. Central spine one, black to whitish with a dark tip, 4-5 mm long, erect. Radial spines 7-8, whitish with dark tips, 5-10 mm (0.2-0.4 in) long, straight. Flowers arising from the bases of axillary tubercles, open during the day, funnelform, yellow, 2-3 cm (0.8-1.2 in) long, 1.8-2.5 cm (0.7-1 in) in diameter; pericarpels woolly but lacking scales. Fruits globose to somewhat elongate, dry at maturity, dull red; perianth parts persistent. Seeds almost globose, with a large hilum, black to brown, pitted. Distribution: a restricted area on limestone rocks in Oaxaca, Mexico.

Ortegocactus macdougallii, photograph by Charles Glass

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