Plants erect, unbranched or branched in basal portion, not deep-seated in substrate. Roots diffuse. Stems unsegmented, bright deep green, hemispheric when young, becoming spheric or ovoid to cylindric, 3.6–12(–20) × 4.5–12 cm, glabrous; ribs 13, spiraling or vertical, slender, crests sinuate, sharp, not interrupted or undulate, narrow; areoles circular or, on older parts of stem, elliptic to ovate, adaxially elongated into short areolar grooves; areolar glands golden, darker with age, cylindric or peglike; cortex and pith firm, not mucilaginous. Spines 11–20 per areole, not obscuring stems, yellowish, whitish, or reddish brown, acicular (rarely central spine flattened), longest spines 12–38 mm; radial spines 10–19 per areole, straight or slightly curved toward stem, longest spines 11–32 mm; central spines 1 per areole, porrect, hooked, terete (rarely flattened). Flowers diurnal, near stem apex, at adaxial edge of areoles or at axillary ends of short areolar grooves, widely funnelform, 3.7–7 × 4–7 cm; outer tepals finely fringed; inner tepals yellow (to ivory) with red bases, 20–25 × 6–9 mm, margins entire, toothed, or lacerate; ovary scaly, hairless, spineless; stigma lobes 5–11, pale yellow to orangish, 3–7 mm. Fruits indehiscent or eventually dehiscent by vertical slits, bright red, spheric or nearly so, ca. 10 × 8–13 mm, fleshy, with 15 or fewer whitish, broad fringed, naked, spineless scales; floral remnant persistent. Seeds black, obovoid, usually 1–1.4 × 0.8–1 mm, minutely papillate; testa cells weakly convex, nearly flat toward proximal end of seed. x = 11.

Distribution

Arid regions, sw United States, Mexico.

Discussion

Species 1.

Hamatocactus has been submerged in Ferocactus or Thelocactus by various authors and grouped with Glandulicactus by others.

Selected References

None.

Lower Taxa

Hamatocactus bicolor