Coryphantha tuberculosa
Cactaceae subfam. cactoideae
cob cactus, white-column foxtail cactus
± diffuse.
diffuse, taproots, or tuberlike, sometimes adventitous.
ovoid to cylindric (spheric), 4–16 × (2.2–)3–6(–6.5) cm;
tubercles (6–)8–11 × 3–6 mm, firm;
areolar glands absent;
parenchyma not mucilaginous;
druses in pith and cortex nearly microscopic, mostly spheric;
pith 1/8–1/4 of lesser stem diam.;
medullary vascular system absent.
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.
(17–)21–41 per areole, ashy white, gray, or pale tan, tips of largest spines pinkish tan to reddish brown or reddish black, all straight;
radial spines 15–41 per areole, gray, (5–)7–12(–13.5) mm, largest spines 0.1–0.2 mm diam.;
subcentral spines 0–6 per areole;
central spines usually 5;
outer central spines (1–)3(–7) per areole, erect or ascending;
inner central spines (0–)2 per areole, porrect or descending, longest spines (5–)10–15(–18) × 0.2–0.3(–0.5) mm.
acicular, subulate, daggerlike, ribbonlike, hairlike, or bristlelike, smooth, rough, striate, or annulate-ridged, glabrous (rarely pubescent), epidermis intact, not separating as sheath.
apical or nearly so, (18–)20–30(–32) × 20–45(–4) mm, sterile distal part of flower tube 5–8.5(–11) mm, longer than stamen-bearing part;
outer tepals conspicuously fringed;
inner tepals 21 per flower, pure white, pale rose-pink, or pale lavender-pink, darker centrally, midstripes ± inconspicuous, (9–)11–19 × 1.5–2.5(–3.5) mm;
outer filaments cream;
anthers pale yellow or nearly white;
stigma lobes 4–6(–8), white, (1.8–)2–4 mm.
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.
bright red [green to maroon], ellipsoid, cylindric, or narrowly obovoid, (8–)13–25 × 3.5–6.5(–7.5) mm, not very succulent;
floral remnant strongly persistent.
dehiscent or indehiscent, depressed-spheric or spheric to long clavate, juicy, fleshy, or dry;
perianth persistent or deciduous.
reddish brown, darker with age, obliquely obovoid, 0.9–1 mm, pitted.
1–3000+, yellowish, reddish, brown, or black, spheric, comma-shaped, lenticular-reniform, pyriform, or obovoid, 0.4–5 mm, rarely strophiolate, never arillate.
= 22 (as C. strobiliformis, C. varicolor, and Escobaria tuberculosa).
Coryphantha tuberculosa
Cactaceae subfam. cactoideae
The names Coryphantha strobiliformis and Escobaria strobiliformis have been misapplied to C. tuberculosa by some recent authors (e.g., L. D. Benson 1982). Those names were based on Echinocactus strobiliformis Poselger, which is C. chihuahuensis (Britton & Rose) A. Berger.
Despite strong superficial similarity to other species in the genus, Coryphantha tuberculosa seems taxonomically isolated. Coryphantha tuberculosa superficially resembles C. sneedii, from which it is distinguished by (1) giant lenticular druses absent (abundant in older pith and cortex of C. sneedii); (2) fruits in region of sympatry always red (green in most U.S. populations of C. sneedii); (3) maximal expansion of flowers in late afternoon, sometimes remaining fully open at sunset (unlike any other species of Coryphantha); (4) flowers larger than those of C. sneedii, either pure white or a characteristic shade of pale lavender-pink, identifiable at a glance when flowers are alive and open; (5) anthers pale yellow, nearly white (bright yellow in C. sneedii); and (6) sterile distal part of receptacular tube longer than the stamen-bearing portion (short in C. sneedii).
On igneous and metamorphic substrates populations of Coryphantha tuberculosa mostly have unbranched stems. D. Weniger (1984) considered such populations to represent C. varicolor Tiegel; their reproductive structures, however, are identical to those of C. tuberculosa. Without seeds or flowers, mature specimens from such populations sometimes are indistinguishable from C. dasyacantha [hence the synonym C. dasyacantha var. varicolor (Tiegel) L. D. Benson].
Coryphantha tuberculosa is the type species of the segregate genus Escobaria, which includes the coryphanthas with pitted seeds.
(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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