Epithelantha micromeris var. micromeris

Common names: Common button cactus
Treatment appears in FNA Volume 4. Treatment on page 240. Mentioned on page 238.

Plants usually unbranched, appearing ashy gray and rough in general aspect. Stems short cylindric to ovoid, (1.3–) 2–3.8 cm diam. Spines 20–35 (–40) per areole, in 1–3 series, mature lateral spine clusters grayish or purplish white with brown bases, collectively appearing as brown spot at center of each spine cluster, 4–5 (–7) mm diam.; longest intact spines near apex of stem 3–12 mm; worn spines 1–3 mm. Flowers partially obscured by longer spines at stem apex, 6–8.5 × 3–4.6 mm; inner tepals 5–8 per flower, (1–) 2.5–3.5 × 1–2 mm; stamens 15–16.2n = 22.


Phenology: Flowering late winter–early spring (Feb–Apr); fruiting late spring–early summer (Apr–Jun).
Habitat: Woodlands, deserts, grasslands, crevices, coarse gravel, cliffs, sedimentary (rarely igneous) substrates
Elevation: 500-1800 m

Discussion

Epithelantha micromeris var. micromeris has the smallest flowers of any cactus species in the flora. Unlike other taxa in this genus, it is autogamous. No hybrids with E. bokei have been found. The spines of var. var. micromeris are never as strongly appressed as on E. bokei except on sexually immature plants less than 15 mm in diameter; those immature plants have the fewest spines.

Selected References

None.

Lower Taxa

None.
0.3 cm3 mm <br />0.003 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
cushionlike +
elliptic +  and circular +
deciduous +  and persistent +
hourglass--shaped +
Allan D. Zimmerman +  and Bruce D. Parfitt +
(Engelmann) F. A. C. Weber ex Britton & Rose +
hardened +
Mammillaria micromeris +
triangular +
not protruding +
proliferating +
flattened +  and cylindric +
Common button cactus +
not mucilaginous +
Ariz. +, N.Mex. +  and Tex. +
500-1800 m +
not separating +
0.6 cm6 mm <br />0.006 m <br /> (0.85 cm8.5 mm <br />0.0085 m <br />) +
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 />) +
3mm;4.6mm +
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 />) +
Woodlands, deserts, grasslands, crevices, coarse gravel, cliffs, sedimentary (rarely igneous) substrates +
0.1 cm1 mm <br />0.001 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
0.23 cm2.3 mm <br />0.0023 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
purplish white +, grayish +  and clusters +
0.4 cm4 mm <br />0.004 m <br /> (0.5 cm5 mm <br />0.005 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 +
Flowering late winter–early spring (Feb–Apr) +  and fruiting late spring–early summer (Apr–Jun). +
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 /> (?) +
Illustrated +
white +  and ashy gray +
straight +
deciduous +  and persistent +
not distinguishable +
20 (?) +  and 35 (?) +
roughened +  and smooth +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
hard +  and rigid +
innocuous +
decurrent +
unsegmented +
4 cm40 mm <br />0.04 m <br /> (6 cm60 mm <br />0.06 m <br />) +
2 cm20 mm <br />0.02 m <br /> (3.8 cm38 mm <br />0.038 m <br />) +
1cm;4cm +
cylindric +  and ovoid +
succulent +
2cm;4cm +
tuberculate +
adventitious +
tuberlike +
epipetric +  and epiphytic +
Epithelantha micromeris var. micromeris +
Epithelantha micromeris +
variety +
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 +