Mammillaria formosa Galeotti ex Scheidw.

국표에는 없다.

Origin and Habitat: Mammillaria formosa is a very widespread and abundant in Mexico in the states of Coahuila, Aguascalientes, Guanajuato, Zacatecas, Tamaulipas, Nuevo Leon and San Luis Potosi.
Altitude: 960-2350 metres above sea level.
Habitat and Ecology: This cactus grows under bushes in xerophytic shrubland, on hills and plains together with Echinocereus pectinatus, Echinocereus stramineus, Mammillaria pilispina, Mammillaria aureilanata, Ariocarpus kotschoubeyanus, Leuchtenbergia principis, Neolloydia matehualensis, Lophophora williamsii, Turbinicarpus klinkerianus, Coryphantha radians, Thelocactus hexaedrophorus,Echinocactus platyacanthus, Ferocactus latispinus, Ferocactus stainesii, Ferocactus histrix, Myrtillocactus geometrizans, Opuntia rastrera, Opuntia imbricacta, Agave lechuguilla, and Agave salmiana. Overgrazing of the habitat by goats is the only threat, but this is not having any real impact on the species. Mammillaria formosa is a very widespread and abundant species with no major threats, but there are some concerns about subspecies pseudocrucigera, which appears to be scarcer than the others.

Common Names include:
ENGLISH: Owl Eyes, Royal Cross
RUSSIAN (Русский): Маммиллярия красивая
UKRAINIAN (Українська): Мамілярія прекрасна, Мамілярія красива, Мамілярія формоза

Description: Mammillaria formosa is a solitary cactus, that ramifies dichotomously with age (occasionally branches also by basal shoots). Given enough time, it will form mounds. Old plants with lots of branching are treasures. This plant variation is huge, the spine length, the wool covering and appearance varies from clone to clone. This species currently comprises four subspecies, the nominate form, subsp. chionocephala (J.A.Purpus) D.R.Hunt, microthele (Muehlenpf.) D.R.Hunt and pseudocrucigera (R.T.Craig) D.R.Hunt. Some people consider Mammillaria formosa subs. chionocephala and Mammillaria formosa subs. microthele to be good species.
Stem: Symmetrically globose at first, later cylindrical, with a depressed apex, 5 - 20 cm high, up to 10 (or more) cm in diameter. Light green,and may, with age, become rubberized at its base.
Tubercles: Crowded, pyramidal, with latex, arranged in numerous, very close-set spirals. The Axil is woolly with white wool especially in the floriferous portion.
Areoles: Oval and woolly when young.
Roots: Fibrous.
Radial spines: 20 - 22, sometimes absent, thin, needle- or bristle-like, sometimes flattened, somewhat horizontal radiating and arranged laterally on each side of the tubercle, white, 3 - 6 mm long.
Central spines: 4 - 7, usually 6, pinkish to brown with darker tips, to 8 mm long.
Flowesr: Diurnal, funnel-form, dull white to light pink about 10 - 15 cm in diameter. Blooms adorn the crown of the plant, usually in a ring, in the growth of the previous year.
Blooming seson: Spring to summer.
Fruits: Attractively deep dull pinkish-red coloured .Club-shaped.
Seeds: Light brown.

Remarks: This is one of the Mammillaria commonly called "Owl Eye Cactus", known for dichotomous branching (forking or dividing into two parts). Although dichotomous branching is not a common occurrence in cacti in general, it happens for some reason in this particular species. What is interesting about this cactus is that it began as a single head, and it has now divided twice, forming what will be four separate branches. When the division process started, it was obvious that four heads would appear, but I don’t think the one head divided quadruply. Most probably, one head became two, and then those two immediately divided.
Other Owl Eye Cactus among others compriseMammillaria karwnskiana, Mammillaria microthele, Mammillaria tlalocii and Mammillaria perbella.

Mammillaria formosa (llifle.com)

https://youtu.be/WWJiSl2DOqE