Escobaría is one of the many genera described by Nathaniel Britton and Joseph Rose (1919-1923) in The Cactaceae, the name honoring Rómulo Escobar of Mexico City and Numa Escobar of Juárez. From its inception, there has been debate whether it is a good genus or should be considered a sub genus of Coryphantha. Several characters, for example, areole structure, suggest that Escobaría is closely related to Coryphantha. On the other hand, there are characters that suggest a closer relationship to Mammillaria than to Coryphantha (David Hunt,pers. comm.).

Those characters that help distinguish Escobaría from Coryphantha are its pitted seeds, fringed outer perianth parts, absence of nectar-secreting glands on the stem, a tendency for older tubercles to become corky and deciduous, flowers usually appearing in spring and of various colors but almost never yellow, and fruits that are indehiscent, red, and naked. Those that distinguish Escobaría from Mammillaria are that its areoles are not developed into separate spine-producing and flower-producing parts, that is, that they are not truly dimorphic, and that flowers arise near the tip of the stem.

Britton and Rose described Neobesseya at the same time they described Escobaría (type, Mammillaria tuberculosa = E. tuberculosa). Most taxonomists believe that the species they placed in Neobesseya more appropriately belong in Escobaría. J. Pinkney Hester described the genus Escobesseya in 1941, but it is clear that the species that he placed in it belong in Escobaría, too. Likewise, in 1976 Hubert Earle proposed the genus Cochiseia for the single species, C. robbinso-rum, but subsequent studies indicate that it also belongs in Escobaría, E. robbinsorum. Two species previously included in Escobaría are now placed in Acharagma. Papers dealing with the controversy surrounding delimitation of Escobaría have been published by Castetter et al. (1975), Eggli (1985), Fischer (1980), Taylor (1983b, 1986), and Zimmerman (1985). Escobaría flowers in spring; the genus includes 23 species.

Escobaría Britton & Rose 1923 Neobesseya Britton & Rose 1923 Escobesseya Hester 1941 Cochiseia W. H. Earle 1976 Escocoryphantha Doweld 1999

Subfamily Cactoideae, tribe Cacteae. Plants low growing, solitary or clustered. Stems depressed globose to cylindrical, lacking nectar-secreting glands. Ribs absent. Tubercles present, often becoming corky and deciduous with age. Areoles elongate, extending from the tubercle tip to its axis. Spines present, usually short, fine, straight, and densely covering the plant. Flowers arising in the upper edge of the areolar groove, often not fully opening; floral tubes short; pericarpels naked; outer perianth parts ciliate on margins. Fruits globose or oblong, usually naked, usually red but sometimes green or pink. Seeds broadly oval to nearly circular, 1.0-1.7mm in diameter, brown orblackish brown, deeply pitted. Distribution: southern Canada south throughout the western United States into northern Mexico, one species in Cuba.

308 Escobaría albicolumnaria

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