Echinocactus horizonthalonius

Lemaire

Cact. Gen. Sp. Nov., 19. 1839.

Common names: Blue barrel cactus visnaga meloncillo
Illustrated
Synonyms: Echinocactus horizonthalonius var. nicholii L. D. Benson
Treatment appears in FNA Volume 4. Treatment on page 189. Mentioned on page 186.

Plants normally unbranched. Stems pale gray-green to bright gray-blue, flat-topped or hemispheric and deep-seated in substrate, 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. Spines (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. Flowers 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. Fruits 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. Seeds 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. 2n = 22.


Phenology: Flowering Apr–Sep.
Habitat: Arid rocky slopes, primarily limestone
Elevation: 600-1700(-2500) m

Distribution

V4 354-distribution-map.gif

Ariz., N.Mex., Tex., Mexico

Discussion

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.

Selected References

None.

Lower Taxa

None.
cushionlike +
confluent +  and spaced +
circular to linear +
deciduous +  and persistent +
nearly circular +  and oblong +
Allan D. Zimmerman +  and Bruce D. Parfitt +
Lemaire +
hardened +
triangular +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
straight +  and curved +
18mm +  and 43mm +
ridged +, flattened +  and terete +
0.1 cm1 mm <br />0.001 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
proliferating +
flattened +  and cylindric +
Blue barrel cactus +  and visnaga meloncillo +
not mucilaginous +
Ariz. +, N.Mex. +, Tex. +  and Mexico +
600-1700(-2500) m +
not separating +
6.5 cm65 mm <br />0.065 m <br /> (9.5 cm95 mm <br />0.095 m <br />) +
5 cm50 mm <br />0.05 m <br /> (7 cm70 mm <br />0.07 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 />) +
5cm;6.5cm +
4 cm40 mm <br />0.04 m <br /> (10 cm100 mm <br />0.1 m <br />) +
dehiscent +  and indehiscent +
persistent +, long +  and deciduous +
10mm;50mm +
spheric +  and ovoid-cylindric +
dry +, fleshy +  and juicy +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
Arid rocky slopes, primarily limestone +
pale tan +  and white +
3 cm30 mm <br />0.03 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 +
entire +  and serrate +
fimbriate +, entire +  and toothed +
deciduous +  and persistent +
Flowering Apr–Sep. +
not mucilaginous +
dehiscent +, , +, rupturing +  and indehiscent +
abscission +
ridgelike +  and nipple--shaped +
Cact. Gen. Sp. Nov., +
curving +
constricted +
prominent +
broadly rounded +  and nearly keeled +
triangular +
arillate +  and strophiolate +
Gray (?) +  and Black (?) +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
dull +  and shiny +
wrinkled +
spheric;obovoid +
1 cm10 mm <br />0.01 m <br /> (3 cm30 mm <br />0.03 m <br />) +
Illustrated +
brown +, tan +, gray +  and pink +
straight +  and curved +
deciduous +  and persistent +
decurved +  and projecting +
5 (?) +  and 8 (?) +
flattened +, subulate +  and annulate-ridged +
2 cm20 mm <br />0.02 m <br /> (5 cm50 mm <br />0.05 m <br />) +
decurrent +
unsegmented +
15 cm150 mm <br />0.15 m <br /> (20 cm200 mm <br />0.2 m <br />) +
pale gray-green +  and bright gray-blue +
4cm;25cm +
deep-seated +
cylindric +, spheric +, hemispheric +  and flat-topped +
succulent +
8cm;15cm +
pinkish +  and olive +
tuberculate +
Echinocactus horizonthalonius var. nicholii +
adventitious +
tuberlike +
epipetric +  and epiphytic +
Echinocactus horizonthalonius +
Echinocactus +
species +
flat +  and convex +
dull +  and glossy +
spinelike +
epiphytic;epiphytic;epiphytic +
not deep-seated +
barrel-shaped +  and spheric +