Epithelantha

F. A. C. Weber ex Britton & Rose

Cact. 3: 92, fig. 102. 1922.

Common names: Button cactus ping-pong ball cactus
Etymology: Greek epi, upon, thele, nipple, and anthos, flower, describing flower position near tubercle apex
Treatment appears in FNA Volume 4. Treatment on page 239. Mentioned on page 99, 255.

Plants miniature, erect, usually unbranched [branched], not deep-seated in substrate. Roots diffuse [tuberlike in E. pachyrhiza of Mexico]. Stems unsegmented, mostly spheric, often flat-topped, 1–4 (–6) × 2–4 (–6) cm, surface completely obscured by spines; tubercles numerous, not confluent into ribs, hemispheric or short cylindric, very small, ca. 1–3 mm; areoles at tips of tubercles, nearly circular, elliptic when distended by flower or fruit, copiously woolly only at sexually mature stem apex; areolar glands absent; cortex and pith not mucilaginous. Spines 20–90 per areole, in 1–5 series, appressed on sides of stems, erect at sexually mature stem apex, white to ashy gray, straight, terete, slender, innocuous, 4.5–12 mm at sexually mature stem apex, often shorter from breakage or wear, smooth or microscopically roughened by breakup of epidermis, not distinguishable as radial and central spines. Flowers diurnal, borne at adaxial margins of spine clusters deep within woolly stem apex, inconspicuous, only distal portion visible from spines and hairs, funnelform, 0.6–1.7 × 0.3–1.7 cm; outer tepals entire or sparsely erose-fimbriate; inner tepals pink to white (rarely yellow), (1–) 2–6 (–9) × 1–2.3 (–3) mm, margins entire or perhaps weakly erose-denticulate; ovary smooth, scales, hairs, and spines absent; stigma lobes (2–) 3–4 (–6), white, to 1 mm. Fruits indehiscent, bright red, narrowly cylindric, 3–20 × 2–3 (–5) mm, weakly succulent, soon drying and papery, smooth, spineless; pulp absent; floral remnant deciduous. Seeds blackish, obliquely hemispheric, 1.2–1.4 × 1 mm, glossy, impressed-reticulate; testa cells flat or slightly convex, anticlinal cell-walls not protruding. x = 11.

Distribution

sw United States, Mexico

Discussion

Species 2–5 (2 in the flora).

In fully adult plants of Epithelantha, the distal portions of the longest spines are worn, leaving all but the apex of the plant covered with short, innocuous spines. Where the ranges of the two species in the flora area overlap, they usually occur on different geologic substrates, although they grow intermingled with no evidence of hybridization, at some sites in Coahuila, Mexico. The interspecific differences have been obscured by published illustrations of misidentified specimens and by inaccurate spine counts.

Although generally resembling Mammillaria and superficially similar to M. lasiacantha, chloroplast DNA evidence somewhat inconclusively indicates that Epithelantha is taxonomically isolated and more closely related to Pediocactus and Ariocarpus than to Mammillaria (C. A. Butterworth et al. 2002).

Selected References

None.

Key

1 Spines 20-35(-40) per areole, in 1-3 superimposed series except for a dense adaxial tuft, grayish or purplish white, often with brown bases collectively forming brown spot at center of each spine cluster; general aspect of stem relatively rough; spine clusters at sides of stem 4-5(-7) mm diam.; flowers 0.6-0.9 × 0.3-0.5 cm Epithelantha micromeris
1 Spines (40-)50-90 per areole, in more than 3 superimposed series, uniformly white to creamy yellow; general aspect of stem appearing smooth and shiny; spine clusters at sides of stem 2- 2.5(-4) mm diam.; flowers 1-1.7 × 1-1.7 cm Epithelantha bokei
... more about "Epithelantha"
cushionlike +
elliptic +  and circular +
deciduous +  and persistent +
hourglass--shaped +
Allan D. Zimmerman +  and Bruce D. Parfitt +
F. A. C. Weber ex Britton & Rose +
hardened +
triangular +
not protruding +
proliferating +
flattened +  and cylindric +
Button cactus +  and ping-pong ball cactus +
not mucilaginous +
sw United States +  and Mexico +
not separating +
Greek epi, upon, thele, nipple, and anthos, flower, describing flower position near tubercle apex +
inconspicuous +
15 cm150 mm <br />0.15 m <br /> (30 cm300 mm <br />0.3 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (15 cm150 mm <br />0.15 m <br />) +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
indehiscent +
persistent +, long +  and deciduous +
3mm;20mm +
cylindric +
papery +  and succulent +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
0.6 cm6 mm <br />0.006 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
0.23 cm2.3 mm <br />0.0023 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
deciduous +  and persistent +
rudimentary +
flat +  and terete +
nearly +  and microscopic +
0 cm0 mm <br />0 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
tuberculate +
fluted;spheric;depressed-spheric or club-shaped +
erose-denticulate +
deciduous +  and persistent +
not mucilaginous +
0.6 cm6 mm <br />0.006 m <br /> (1.7 cm17 mm <br />0.017 m <br />) +
0.3 cm3 mm <br />0.003 m <br /> (1.7 cm17 mm <br />0.017 m <br />) +
ridgelike +  and nipple--shaped +
3;2;2;30 +
triangular +
arillate +  and strophiolate +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
0.12 cm1.2 mm <br />0.0012 m <br /> (0.14 cm1.4 mm <br />0.0014 m <br />) +
hemispheric +
1 cm10 mm <br />0.01 m <br /> (?) +
white +  and ashy gray +
straight +
deciduous +  and persistent +
not distinguishable +
20 (?) +  and 90 (?) +
roughened +  and smooth +
0.45 cm4.5 mm <br />0.0045 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
hard +  and rigid +
innocuous +
decurrent +
unsegmented +
4 cm40 mm <br />0.04 m <br /> (6 cm60 mm <br />0.06 m <br />) +
1cm;4cm +
flat-topped +  and spheric +
succulent +
2cm;4cm +
tuberculate +
adventitious +
tuberlike +
epipetric +  and epiphytic +
Epithelantha +
Cactaceae subfam. Cactoideae +
convex +  and flat +
dull +  and glossy +
not confluent +
cylindric +, short +  and hemispheric +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
epiphytic;epiphytic;epiphytic +
not deep-seated +
barrel-shaped +  and spheric +