Echinocactus horizonthalonius
Cactaceae subfam. cactoideae
biznaga-tonelmancamula, blue barrel cactus, devilshead, silverbell cactus, Turk's head cactus, visnaga meloncillo
diffuse, taproots, or tuberlike, sometimes adventitous.
pale gray-green to bright gray-blue, flat-topped or hemispheric and deep-seated in sub-strate, spheric with age or stoutly short cylindric (remaining hemispheric at high elevations), 4–25(–45) × 8–15(–20) cm;
ribs (7–)8(–9), vertical to helically curving around stem, rib crests broadly rounded, uninterrupted or slightly constricted between areoles.
segmented or unsegmented, usually conspicuously succulent with thick cortex and pith, surface usually ribbed or tuberculate, usually somewhat woody with wood confined to internal ring, bark sometimes becoming proximally hardened and woodlike;
areoles circular to linear [protracted into finger-shaped shoots in Neoraimondia of South America], hourglass-shaped in some genera, with spiny portion separated from flowering portion by a groove in the stem surface, spiny areoles completely separate from flowering areoles in some genera, bearing 0–90 spines, glochids absent.
absent or rudimentary and microscopic or nearly so, less than 1 mm.
(5–)8(–10) per areole, loosely projecting or strongly decurved, pink, gray, tan, or brown, strongly annulate-ridged, subulate, ± flattened, glabrous, generally not hiding stem surface;
radial spines 5(–8) per areole, similar to central spines;
central spines 1(–3) per areole, 18–43 × 1–2.5(–3) mm, longest spine usually descending, straight or decurved throughout its length.
acicular, subulate, daggerlike, ribbonlike, hairlike, or bristlelike, smooth, rough, striate, or annulate-ridged, glabrous (rarely pubescent), epidermis intact, not separating as sheath.
5–7 × 5–6.5(–9.5) cm;
inner tepals bright rose-pink or magenta, color ± uniform from base to apex, 3 × 1.5 cm, margins entire to serrate;
stigma lobes pinkish to olive.
diurnal to nocturnal, bisexual (rarely unisexual or functionally so), solitary in areoles (rarely several), radially symmetric (rarely bilateral), sessile, broadly salverform, urceolate, funnelform, or long tubular;
flower tube epigynous, usually conspicuous, adnate to upward extension of stem surrounding ovary, 0.2–15[–30] cm;
triangular leaflike bracts or small scales sometimes present on ovary and flower tube;
nectary often apparent, forming open chamber surrounding base of style.
indehiscent or weakly dehiscent through basal abscission pore, pink or red, spheric to ovoid-cylindric, surfaces partly or entirely hidden by hairs from axils of scales and long areolar hairs of stem apex, usually quickly drying to tan shell before seed dispersal, 10–30 mm;
scales several, tips dark, spinelike, glabrous.
dehiscent or indehiscent, depressed-spheric or spheric to long clavate, juicy, fleshy, or dry;
perianth persistent or deciduous.
black or gray, angular or slightly wrinkled, spheric to obovoid, 2–3 mm;
testa cell surfaces slightly convex, with weak network pattern of slightly protruding anticlinal cell walls.
1–3000+, yellowish, reddish, brown, or black, spheric, comma-shaped, lenticular-reniform, pyriform, or obovoid, 0.4–5 mm, rarely strophiolate, never arillate.
= 22.
Echinocactus horizonthalonius
Cactaceae subfam. cactoideae
The Sonoran Desert populations of Echinocactus horizonthalonius have been segregated as var. nicholii, but are relatively similar to plants in New Mexico and extreme western Texas. Much greater morphologic diversity exists farther east and in Mexico, where shorter-spined, nearly flat-topped plants, which are more distinctive than the Sonoran Desert populations, have escaped taxonomic distinction.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera ca. 111, species ca. 1500 (28 genera, 121 species in the flora).
Subfamily Cactoideae is the most diverse group of the Cactaceae, in terms of size, architecture, habitat, and habit. The vast majority of North American species are xerophytic, with columnar to spheric or barrel-shaped stems. A few are geophytic, that is, stems are mostly deep-seated in the soil substrate, often with the plant consisting mostly of an enlarged taproot and the visible parts of the stems appearing nearly flush with the soil surface or nearly buried during drought, becoming taller and slightly more conspicuous only during the growing season. Fewer species still, are epiphytic, and those only in the tropical and subtropical regions of North America and South America.
In the following treatments, most authors have attempted to recognize varieties wherever current evidence is compelling. Where evidence is equivocal, our tendency has been to include greater variability within varieties and, hence, fewer formal trinomials. Unfortunately, in the absence of strong supporting evidence, herbarium specimens of cacti are usually inadequate for the purpose of making taxonomic decisions. As a consequence, some populations of conservation interest here have been placed into synonmy before critical studies have been conducted to determine quantitatively and objectively how distinct each population is, or which deserve varietal status. Authors do not intend to imply that other varieties should not eventually be recognized. More systematic work, including DNA research and field research of all variants, is needed as a prelude to reassessing the status of currently listed and proposed populations. Such populations need to be protected during the entire phase of analysis and reassessment.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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