Xerophyte

Central Spines

Usually one (only in older specimens), sometimes absent, erect, straight or slightly curved downward, 11-16(-20) mm long, from all the upper areoles.

Seeds

Small, orange, drying to brown, spheric to comma-shaped, 1.1-1.7 mm, finely and weakly raised-reticulate.

Description

Coryphantha nickelsiaeSN|10068]]SN|10084]] (Mamillaria nickelsae) is a solitary to densely cespitose cactus species, forming low mats with the stems nearly hidden by overlapping numerous, fine spines. Older specimens often have characteristic ribbonlike uppermost radial spines. Some authors consider this taxon to be a variety of Coryphantha sulcataSN|10084]]SN|10068]] (see Hunt et al. 2006).

Roots

Roots diffuse or short taproots; branches root adventitiously.

Note

The epithet "nickelsiae" honors the Texas cactus collector Anna B. Nickels.

Tubercles

Bluntly conical, firm, rather broad at base, low, not densely arranged,soft, to 7-10(-13) mm long, becoming quite as broad and imbricated, almost hidden by the overlapping spines, sometimes with glands among the spines. Areolar glands seasonally conspicuous.

Flowers

Flowers apical or nearly so, light yellow, 4.5-5(-7) cm in full expansion. Inner perianth-segments ca. 30 per flower, spreading, linear-lanceolate, acuminate, ca. 30 mm long. Outer perianth-segments entire. Filaments white or pale yellow. Anthers yellow to orange-yellow. Stigma lobes 5-8, white or cream, 2.5-8 mm long. This species flowers in summer (August to September).

Stem

Deep-seated, aerial portion hemispheric or hemispherical or globose more or less flat-topped, tuberculate, pale to dark green and glaucous, 4 to 11 cm high tall, (4-)5-7 cm in diameter; older plants becoming purplish. Solitary (especially in western part of the range) or often branched from the axils of the lower tubercles near the surface of the ground and forming mats (mainly in the eastern part of the range).

Radial Spines

(13-)14-16(-20), crowded, slender, white, 8-23 mm long, at first simply spreading but afterwards bent back and interlaced with those of adjoining tubercles. The lowermost radial spines 8-10 mm long, the upper ones, at least on old plants, often longer, stouter, extending into the groove and forming a fascicle, the clustered fascicles making an upright tuft at the vertex, slender. All spines at first yellowish at base with dark reddish-brown tips, but afterwards bleaching white, others brownish to nearly black throughout.

Fruits

Nearly globular, or ellipsoid, grey-green or bright green (paler at base), (5-)18-23 mm long, 8-10 mm wide. Floral remnant strongly persistent.