One of the most impressive groups of low-growing cacti in the southwestern United States and northern Mexico is also one of the most difficult to propagate. Considerable field-work has been done on this group, but researchers are divided as to the correct boundaries of the genera. In general, scientists in the United States and Mexico believe that the group consists of two genera, Sclerocactus and Echinomas-tus, whereas many Europeans believe that Sclerocactus should include the species of both. Kenneth Heil and J. Mark Porter (1994) extensively investigated Sclerocactus in the field and published an important paper, which defined the genus rather narrowly, excluding the species placed in the genera Ancistrocactus, Echinomastus, Glandulicactus, and Toumeya by Britton and Rose. However, they did include Coloradoa mesa-verdae (= S. mesa-verdae) in their study. Most researchers agree that many of the species placed in those genera by Britton and Rose belong in Sclerocactus, though David Ferguson (1991) argued that Glandulicactus should be retained as a separate genus. Porter (1999), using DNA sequencing and morphological data, has concluded that the broadly defined Sclerocactus of the International Cactaceae Systematics Group should be subdivided and Echinomastus recognized as a distinct genus. Therefore, Echinomastus is treated separately here, based on the work of Porter and my own field studies. Fritz Hochstatter, a German hobbyist, has traveled extensively throughout North America studying Sclerocactus. His numerous publications (Hochstatter 1990, 1996-1997) differ in several ways from the study by Heil and Porter (1994). The International Cactaceae Systematics Group has adopted some of Hochstatter's combinations, some of which are included in the treatment here.

Nathaniel Britton and Joseph Rose described Sclerocactus (type, Echinocactuspolyancistrus = S. polyancistrus) in 1922. They noted that the genus is similar to Ferocactus but that the fruit is nearly naked and the scales bear small tufts of wool in their axils. The name Sclerocactus is derived from the Greek scleros, hard or cruel and referring to "the formidable hooked spines which hold on in a most aggravating manner" (Britton and Rose 1919-1923, 3: 212). The 14 species of Sclerocactus flower during spring. Many have restricted distributions and most populations have been adversely affected by illegal collecting.

Sclerocactus Britton & Rose 1922 Toumeya Britton & Rose 1922 Ancistrocactus Britton & Rose 1923 Glandulicactus Backeberg 1938 Coloradoa Boissevain & Davidson 1940

Subfamily Cactoideae, tribe Cacteae. Plants low growing, mostly single but occasionally clumped. Stems globose to cylindrical, rarely flat-topped, tuberculate or ribbed, spiny. Areoles more or less extended beyond the spine-bearing portion, often with nectar glands. Central spines 1-6, sometimes absent, variable in color, one or more hooked, to 9 cm (3.5 in) long. Radial spines 2-11, usually white or gray, sometimes darker, straight, to 6 cm (2.4 in) long. Flowers arising at the stem tips, open during the day, short funnelform or bell shaped; pericarpels and floral tubes naked. Fruits ovoid, cylindrical, club shaped, or barrel shaped, usually scaly, fleshy and indehiscent or becoming dry and dehiscing in various ways; perianth parts persistent. Seeds broadly oval, brown or blackish brown, shiny or dull, keeled or not, with some surface relief. Distribution: southwestern United States and northern Mexico.

Sclerocactus brevihamatus (Engelmann) D. R. Hunt 1991 TOBUSCH FISHHOOK CACTUS

Echinocactus brevihamatus Engelmann 1856, Ancistrocactus brevihamatus (Engelmann) Britton & Rose 1923, Pediocactus brevihamatus (Engelmann) Halda 1998 Mammillaria tobuschiiW.T. Marshall 1952, Ancistrocactus tobuschii (W. T. Marshall) L. D. Benson 1966, Ferocactus tobuschii (W. T. Mar shall) N. P. Taylor 1979, Sclerocactus brevihamatus subsp. to-buschii (W. T. Marshall) N. P. Taylor 1995, Pediocactus brevihamatus subsp. tobuschii (W.T. Marshall) Halda 1998, A. scheerisubsp. tobuschii (W.T. Marshall) Doweld 1999

Plants usually solitary, globose to obovoid, dark green, 5-10 cm (2-3.9 in) high, 5-8 cm (2-3.1 in) in diameter. Ribs 1012. Tubercles with woolly grooves their entire length, 6-12 mm (0.2-0.5 in) high. Central spines usually 4, lowermost one horizontally extended and hooked, whitish, flattened, 25-45 mm (1-1.8 in) long. Radial spines 7-14, white, spreading, round, 10-20 mm (0.4-0.8 in) long. Flowers funnel-form, greenish white to light yellow to creamy white, with a purple tint, 2.5-3 cm (1-1.2 in) long. Fruits thin walled, about 15 mm (0.6 in) long, nearly naked. Distribution: southern Texas.

Two subspecies of Sclerocactus brevihamatus are recognized. Subspecies tobuschii differs from subspecies brevihamatus in having a nearly flat body, 7-9 irregularly spreading radial spines, and light yellow to cream flowers; it occurs only on the Edwards Plateau and is listed (as Ancistrocactus tobushii) as endangered in the U.S. Endangered Species Act and is included (as S. brevihamatus var. tobushii) in Appendix I of cites.

Sclerocactus glaucus (K. Schumann) L. D. Benson 1972 uinta basin hookless cactus

Echinocactusglaucus K. Schumann 1898, Pediocactus glaucus (K. Schumann) Arp 1972, Ferocactus glaucus (K. Schumann) N. P.Taylor 1979

Sclerocactus wetlandicus Hochstatter 1989, Pediocactus wetlandicus

(Hochstatter) Halda 1998 Sclerocactus wetlandicus subsp. ilseae Hochstatter 1993 Sclerocactus brevispinus K. D. Heil &J. M. Porter 1994

Plants mostly solitary. Taproots much branched. Stems globose to cylindrical, blue-green, spines not obscuring the stems, 3-12 cm (1.2-4.7 in) high, 4-9 cm (1.6-3.5 in) in diameter. Ribs 12-13. Tubercles protruding 6-9 mm (0.2-0.4 in) above the ribs. Central spines 1-3, whitish to brownish, 12-26 mm (0.5-1 in) long, elliptic in cross section, mostly straight but sometimes slightly curved or hooked. Radial spines 2-6, whitish, 6-17 mm (0.2-0.7 in) long, similar to the centrals. Flowers wide funnelform, pink, 3-4 cm (1.2-1.6 in) long, 4-5 cm (1.6-2 in) in diameter. Fruits barrel shaped, 9-12 mm (0.4-0.5 in) long. Distribution: eastern Utah and southwestern Colorado. Sclerocactus glaucus is listed as threatened in the U.S. Endangered Species Act and is included in Appendix I of cites.

Continue reading here: Sclerocactus mesaeverdae Boissevain Davidson ex

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