Its appeal is in the strange lime-grey-green
epidermis and short black spines.
 

Description:  Clumping small cactus that slowly form great bushes.
Stems: This species has a strange and unmistakable lime-green-grey coloured epidermis, each stem extends with the years, of 3 to 4 cm of diameter.
Tubercles: Low, often squashed, rhomboid and arranged in spiral, of 8 to 10 mm of diameter.
Areoles: Dimorphic, with white felt and spines in the superior part, some times with furrows.
Central spines: 1 turgid black, or whitish with a black tip 4 to 5 mm in length.
Radial spines: 7 to 8 radial spines of the same color of 5-10mm of length.
Flowers: Diurnal, funnel-shaped yellow 2 to 3 cm long , and 2, 5-3 (5) cm of diameter in the spring or summer, arises from the base of the areoles of superior tubercles, They last a couple of days. It is an auto-fertile plant.
Fruit: Globular, slightly extendended, dry when mature, reddish, of about 5 mm of diameter, conserves adhered rest of perianth, indehiscent.
Seed: Almost spherical, brown blacks 1.2 mm in length and 0.9 mm wide, of a shining black colour.

Cultivation: Not the easiest of plants to grow well and tricky to grow when on its own roots, this interesting and distinctive looking plant needs a little care with regard to heat and water. It show a distinct intolerance to over watering either by rotting off, or by bursting of the epidermis. Composts should therefore be very open and gritty, use shallow pots, with good drainage.. To prevent growing a monster totally out of proportion to their attractive and natural form, one should limit the fertiliser.
A harmless but unsightly orange discoloration (corkiness) is common at the base of the stems, though this is not due to disease, and apparently is unavoidable, cautious examination should periodically be undertaken to ensure that rot has not set in Re-rooting is not easy.

Propagation: Very slow from seed. Many authors recommend grafting, first on Pereskiopsis and soon on Myrtillocactus geometrizans. If it does not reject the stock, it is possible to be cultivated without problems. If we prefer to cultivate it on its own roots, we can maintain intact its characteristics without deformities, grafted plants clump readily and the offsets can be used for make cuttings.

Scientific name:  Ortegocactus macdougallii Edward Alexander1961,

Synonyms: Neobesseya macdougallii

Origin:  Mexico (Oaxaca) , San Jose Lachuguiri, in a small practically inaccessible zone.

Habitat:  Grows in an escarped limestone stone rock top, practically deprived of trees and scrubs, at a height of 2000 meters

Conservation status: Listed in CITES appendix 2.

Etymology: It is called thus in honour of the family Ortega, from San Jose Lachuguiri that helped Tom MacDougall in the discovery of this plant.

Ortegocactus macdougalli is a genus closely related to Mammillaria. This is the sole species of the genus Ortegocactus (monospecific). Recent philogenetic studies on of the DNA locate the Ortegocactus between Neolloydia and Coryphantha.