La particolarità di questa specie sono i numerosi rami che radicano autonomanente. Questi si affrancano presto dalla pianta madre con la quale sono connessi in maniera effimera. In poco tempo si forma una piccola colonia di piante indipendenti.

Family: Cactaceae (Cactus Family)

Scientific name:  Mammillaria thornberi Orcutt
Place of publication: W. Amer. Sci. 12:161. 1902

Origin:  These cacti are typically found in Arizona and Mexico (Sonora)

Habitat:  Sonoran desert scrub, valley floors, silty or sandy soils; 10-600 m. . It will grow only where it is shaded from the full sun.  This can be under shrubs and frequently at the base of Opuntias, where the germinating seeds find added protection provided by the numerous fallen opuntia joints.

Common Names include: Thornber's Fishhook Cactus, Thornber's nipple cactus, clustered Fishhook Cactus, clustered pincushion, slender pincushion, organ pipe.

Etymology: Named after Prof. John Thornber (1872-1962) US- American botanist at the university of Arizona

Conservation status:  Listed in CITES appendix 2.

Synonyms:

• Mammillaria fasciculata Britton & Rose 1923, misapplied, not Engelmann ex B.D. Jackson 1895 (see Echinocereus fasciculatus)
• Neomammillaria fasciculata
• Cactus fasciculatus
• Ebnerella fasciculata (Britton & Rose) Buxbaum 1951
• Chilita fasciculata (Britton & Rose) Buxbaum 1954
• Mammillaria yaquensis R.T. Craig 1945
• Ebnerella yaquensis (R.T. Craig) Buxbaum 1951
• Chilita yaquensis (R.T. Craig) Buxbaum 1954
• Mammillaria thornberi ssp. yaquensis (R.T. Craig) D.R. Hunt 1997

The epithet fasciculata was long misapplied to Mammillaria thornberi.  It correctly pertains to Echinocereus fasciculatus (Engelmann) L. D. Benson.

Mammillaria thornberi

Description: M. thornberi is a small cactus with slender stems, that likes to cluster from the base, forming nice clumps or families. The particularity of this species is that every branch will form an independent root system, the connections of which to the rest of clone are ephemeral, resulting in dense clumps of independently rooted stems.
Roots:  Diffuse, upper portion not enlarged.
Stems: Slender, cylindrical, often dull purplish green, 4.5-10 cm tall (but sometime 30 cm high), 2-3.5 cm in diameter, tapered at base, firm, lateral joints easily detached from the body.
Tubercles: Flabby, purplish green, short conical to cylindrical. 5-9 × 5-9 mm; axils appearing naked or slightly woolly; cortex and pith not mucilaginous; latex absent.
Parastichy number: 5-8
Spines: Usually 14-22 per areole, whitish to yellowish near base, pale reddish brown to nearly black toward tips, glabrous; They do not hide the surface of the stem completely.
Radial spines: 13-21 per areole, whitish, with reduced dark tips relative to central spines, bristlelike, 5-9 mm long, stiff.
Central spines: Small, fish-hooked, usually 1 (or sometime 2 or 3) per areole, porrect, often more elongated, darker, 9-18 mm long.
Subcentral spines: 0(-3) per areole, adaxial to central spines, more or less transitional to radial spines.
Flowers: Broadly funnel-form, light pink on the outside and a deeper lavender pink in the center, with a white star shape appearance from a distance, due to the contrast of colors, 1.5-3 long and 1-2.5 cm large.  The outermost tepal margins are densely short-fringed.
Blooming season (In Europe): Apr-May, July-Aug.
Fruits: Prominent, bright red, obovoid to nearly clavate, 7-15 × 4-7 mm, juicy only in fruit walls; floral remnants persistent.  Fruiting in Oct-Nov, Feb-Mar.
Seeds: Black, 0.9-1.1 × 0.8-1.1 × 0.7 mm, pitted.

The subspecies 'thornberi' has thicker stems, 2,5 cm wide and tapered at the base, with 15-20 radial spines. The radial spines are not distinctly pubescent. It o,ccurs in Arizona and Sonora.
The subspecies 'yaquensis' has more fragile stems at 1,5 cm thick and 7 cm long, with 18-19 minute, soft, and hairy radial spines. It is endemic to Sonora.