Origin and Habitat: Southern USA ( Texas, New Mexico, Utah, California and Arizona) and Mexico (Chihuahua Sinaloa, and Sonora)
Type locality: "On the Gila, 3,000 to 4,000 feet above the sea."
Altitude: It grows at elevations from 300 to 1,500 metres above sea level.
Habitat: It is wide-ranging and abundant in sandy plains, gravelly slopes, and rocky ridges in xerophyllous scrub and grasslands.
Ecology: This plants uses nurse plants to protect against frosts, harsh sun, trampling, etc. so one must look carefully under shrubs and trees to find them. In the same area it is possible to find several cactus and succulent species like: Echinocactus parryiSN|938]]SN|938]], Echinocereus fendleriSN|8503]]SN|7149]], Echinocereus pectinatusSN|7149]]SN|8503]], Coryphantha recurvataSN|10231]]SN|10231]], Lophocereus schottiiSN|8344]]SN|8344]], Pachycereus pecten-aboriginumSN|8498]]SN|8498]], Stenocereus thuberi, Opuntia fulgida, Opuntia leptocaulisSN|25092]]SN|10936]], Opuntia engelmanniiSN|19920]]SN|19920]], Opuntia violaceaSN|10936]]SN|25092]], Opuntia bigelowii, Ferocactus wislizeniSN|21495]]SN|16130]]i, Carnegiea giganteaSN|6374]]SN|6374]], Ferocactus acanthodesSN|10113]]SN|10113]], Ferocactus emoryiSN|16130]]SN|21495]], Ephedra trifurca, Agave palmeriSN|22538]]SN|22538]], Yucca elata, and Fouquieria macdougaliiSN|11333]]SN|11333]].

• Mammillaria microcarpa Engelm. in Emory
• Chilita microcarpa (Engelm. in Emory) Buxb.
• Ebnerella microcarpa (Engelm. in Emory) Buxb.
• Neomammillaria microcarpa (Engelm. in Emory) Britton & Rose

• Mammillaria grahamii Engelm.
• Cactus grahamii (Engelm.) Kuntze
• Chilita grahamii (Engelm.) Orcutt
• Cochemiea grahamii (Engelm.) Doweld
• Coryphantha grahamii (Engelm.) Rydb.
• Mammillaria microcarpa subs. grahamii (Engelm.) Mottram
• Mammillaria milleri var. grahamii (Engelm.) Neutel.
• Mammillaria microcarpa Engelm. in Emory
• Chilita microcarpa (Engelm. in Emory) Buxb.
• Ebnerella microcarpa (Engelm. in Emory) Buxb.
• Neomammillaria microcarpa (Engelm. in Emory) Britton & Rose
• Mammillaria microcarpa var. auricarpa W.T.Marshall
• Mammillaria microcarpa f. auricarpa (W.T.Marshall) Neutel.
• Mammillaria milleri f. auricarpa (W.T.Marshall) Neutel.
• Mammillaria microcarpa f. cristata hort.
• Mammillaria milleri (Britton & Rose) Boed.
• Chilita milleri (Britton & Rose) Orcutt
• Mammillaria microcarpa var. milleri (Britton & Rose) W.T.Marshall
• Neomammillaria milleri Britton & Rose
• Mammillaria oliviae Orcutt
• Chilita oliviae (Orcutt) Orcutt
• Ebnerella oliviae (Orcutt) Buxb.
• Mammillaria grahamii var. oliviae (Orcutt) L.D.Benson
• Mammillaria microcarpa f. oliviae (Orcutt) Neutel.
• Mammillaria milleri f. oliviae (Orcutt) Neutel.
• Neomammillaria oliviae (Orcutt) Britton & Rose

• Mammillaria grahamii subs. sheldonii (Britton & Rose) D.R.Hunt
• Chilita sheldonii (Britton & Rose) Orcutt
• Cochemiea sheldonii (Britton & Rose) Doweld
• Ebnerella sheldonii (Britton & Rose) Buxb.
• Mammillaria microcarpa var. sheldonii (Britton & Rose) Neutel.
• Mammillaria milleri var. sheldonii (Britton & Rose) Neutel.
• Mammillaria sheldonii (Britton & Rose) Boed.
• Neomammillaria sheldonii Britton & Rose
• Mammillaria alamensis R.T.Craig
• Chilita alamensis (R.T.Craig) Buxb.
• Escobariopsis sinistrohamata (Boed.) Doweld
• Neomammillaria alamensis (R.T.Craig) Y.Itô
• Mammillaria gueldemanniana Backeb.
• Chilita gueldemanniana (Backeb.) Buxb.
• Mammillaria microcarpa f. gueldemanniana (Backeb.) Neutel.
• Mammillaria milleri f. gueldemanniana (Backeb.) Neutel.
• Mammillaria gueldemanniana var. guirocobensis (R.T.Craig) Backeb.
• Ebnerella guirocobensis (R.T.Craig) Buxb.
• Mammillaria guirocobensis R.T.Craig
• Mammillaria inaiae R.T.Craig
• Chilita inaiae (R.T.Craig) Buxb.
• Ebnerella inaiae (R.T.Craig) Buxb.
• Neomammillaria inaiae (R.T.Craig) Y.Itô
• Mammillaria marnieriana Backeb.
• Mammillaria pseudoalamensis Backeb.
• Mammillaria swinglei (Britton & Rose) Boed.
• Chilita swinglei (Britton & Rose) Orcutt
• Chilita swingleri (Britton & Rose) Orcutt
• Cochemiea swinglei (Britton & Rose) Doweld
• Ebnerella swinglei (Britton & Rose) Buxb.
• Mammillaria microcarpa f. swinglei (Britton & Rose) Neutel.
• Mammillaria milleri f. swingeli (Britton & Rose) Neutel.
• Neomammillaria swinglei Britton & Rose

Description: Mammillaria microcarpaSN|9210]]SN|9210]] has long been a favorite in living collections. It is sensitive to any excess of moisture and does not do well in cultivation, but will reward the skilled growers with ring of fine rose-purple flowers circling the crown of the plant. This plant is generally known under the name of Mammillaria grahamiiSN|9189]]SN|9189]]. This species is quite common in habitat, but variable throughout the region.
Habit: Simple or budding either at base or near middle, often cespitose, but in small clusters, sometimes 20 cm high.
Roots: Thickened.
Stem: Globose, conical to short cylindric, light green, up to 20 cm tall (but usually only 7-8 cm), 2,5-8(-11) cm in diameter.
Tubercles: Small, ovoid to cylindrical, often bases four-angled or flattened from side to side when old, corky when old. Without latex.
Areoles: Dimorphic. The spinous portion, at the tip of the tubercle, is small round or oval, with some white wool at first, but later bare. The floral or vegetative part in the axil is without wool, so the axils are naked.
Radial spines: 15 to 35, radiating evenly from the areole, lying flat upon the surface of the plant, interlocking with those of neighboring areoles and nearly hiding flesh of plant, straight, needle-like, white, sometimes with dark brown to reddish tips, slender, rigid, glabrous, 6 to 12 mm long, lateral ones longest. The upper centrals stand up-right just in front of the upper radials, forming a V if there are two of them, but there may be only one.
Central spines: 1 to 3, yellowish-brown, dark-brown to purplish black, when more than one the lower stouter, 12-25 mm long, the longest one usually hooked and standing out perpendicular to the plant surface.
Flowers: Forming a ring around the new growth near top of plant, 2 to 4,5 cm long, broadly funnel-shaped, opening widely, pink, lavender-pink or reddish purple, sometimes white. Outer perianth segments ovate, obtuse, or conical with brownish midlines and short-ciliate margins; inner perianth-segments longer purplish, slender, sometimes with whitish margins, obovate, acuminate. Filaments pink; anthers pale orange. Style longer than stamens, up to 6 mm long above the stamens, purplish; stigma-lobes 6 or 10, linear, light green.
Fruit: Subglobose to clavate, 12 to 25 mm broad, scarlet, with the dried flower parts remaining upon them. These fruits develop rather slowly, there is a long blooming season, and those started late in the summer remain as small, green, oval structures under the spines until during the winter they dry up without ripening properly at all. For this reason fruits have sometimes been called dimorphic.
Seeds: Black, shining, pitted, almost globose, 0,8 to 1 mm in diameter.
Notes: The degree of difference between Mammillaria grahamiiSN|9189]]SN|9189]] and Mammillaria microcarpaSN|9210]]SN|9210]] is still a matter for debate.

Bibliography: Major references and further lectures
1) Pilbeam J., “The Cactus file, Mammillaria” 6: 120, Cirio Pub. Services, 01/Dec/1999
2) John Pilbeam “Cacti for the Connoisseur: A Guide for Growers & Collectors” Timber Press, 01/lug/1987
3) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
4) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
5) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
6) Brian Loflin, Shirley Loflin “Texas Cacti: A Field Guide” Texas A&M University Press, 26/ott/2009
7) Forrest Shreve, Ira Loren Wiggins “Vegetation and Flora of the Sonoran Desert” Volume 1 Stanford University Press, 1964
8) Heil, K., Terry, M. & Corral-Díaz, R. 2013. Mammillaria grahamii. In: IUCN 2013. “IUCN Red List of Threatened Species.” Version 2013.2. <www.iucnredlist.org>. Downloaded on 11 January 2014.
9) Del Weniger “Cacti of the Southwest: Texas, New Mexico, Oklahoma, Arkansas, and Louisiana” University of Texas Press, 1969
10) Ulises Guzmán, Salvador Arias, Patricia Dávila: “Catálogo de cactáceas mexicanas.” Universidad Nacional Autónoma de México, Mexico state. 2003
11) Urs Eggli, Leonard E. Newton “Etymological Dictionary of Succulent Plant Names” Springer, Berlin/Heidelberg 2010

Cultivation and Propagation: This plant is not famous for being easy to cultivate, but in good conditions with excellent ventilation, it grows without difficulty. It is especially sensitive to over-watering. So careful watering and an open mineral potting soil are a must. Avoid the use of peat or other humus sources in the potting mixture. Don't add limestone to the potting mix, which must be moderately acidic. It can be sensitive to frost (but some population are resistant to -10° C). It requires maximum sun exposure to reach its full potential, and to achieve success in flowering. A winter rest that allows the plant to shrivel (perhaps losing up to 25% of its summer height) will encourage flowering and long time survival. Be careful to encourage slow growth.
Propagation: Seeds or offsets.
Uses:
- Apache, Pima, Chiricahua & Mescaleros: They used the fresh and dried fruit primarily for children, as a snack food..
- Pima: They used the boiled plant placed warm in the ear for earaches and suppurating ears.
- Seri And Pima also used it in special ceremonies by shamans. Fruits are also said to produce hallucinatory effects.