Coryphantha tuberculosa
Coryphantha dasyacantha
cob cactus, white-column foxtail cactus
Big Bend cactus
± diffuse.
diffuse (rarely short taproots).
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.
spheric, becoming short cylindric in age, 4.5–10(–17) × (2–)3–4.5(–6) cm (1–3 × 2–5 cm in Davis Mountains, Texas);
tubercles (4–)7–8(–12) × 3–5(–7) mm, moderately soft;
areolar glands absent;
parenchyma not mucilaginous, medullary vascular system absent.
(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.
26–42 per areole, white with red-brown to nearly black tips (brown to reddish brown with black tips in Davis Mountains);
radial spines 21–31 per areole (12–22 in Davis Mountains), 6–9(–10) mm;
subcentral spines several, appressed;
central spines (3–)4–9(–11) per areole (2 in Davis Mountains), spreading, straight, longest spines 12–17 × 0.2–0.3(–0.4) mm.
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.
nearly apical, 15–30 × (10–)13–15(–22) mm, sterile distal part of flower tube 0–2 mm, shorter than stamen-bearing part;
outer tepals conspicuously fringed;
inner tepals 14 per flower, midstripes pinkish to brown or brownish green, proximally white, (7–)8–10(–12) × 1.5–3 mm;
outer filaments white or colorless;
anthers bright yellow;
stigma lobes 4(–6), dark green to bright yellow, 1–2.5 mm.
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.
bright red, clavate, cylindric, or narrowly ellipsoid, (7–)13–27(–35) × 3.5–6(–7) mm, not very succulent;
floral remnant strongly persistent.
reddish brown, darker with age, obliquely obovoid, 0.9–1 mm, pitted.
black, subspheric, 1–1.2 mm, pitted.
= 22 (as C. strobiliformis, C. varicolor, and Escobaria tuberculosa).
= 22.
Coryphantha tuberculosa
Coryphantha dasyacantha
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.)
Many published photographs and specimen citations purported to represent Coryphantha dasyacantha reflect misidentifications. Ripe fruits, with their strongly persistent floral remnant, provide the only simple way to distinguish C. dasyacantha from C. duncanii. The black fresh seeds of C. dasyacantha and related species usually provide immediate distinction from C. tuberculosa, C. sneedii, and C. vivipara, which have differently shaped, bright reddish brown fresh seeds. In addition, the greenish stigma lobes of C. dasyacantha, C. duncanii, C. chaffeyi, C. pottsiana, and certain Mexican taxa contrast with the violet or white stigma lobes of C. vivipara, C. sneedii, C. alversonii, and C. hesteri. Vegetatively, C. dasyacantha always is distinguishable from C. vivipara and C. sneedii by its lack of the unusually large druses described under 20. C. sneedii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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