Autor: Britton & Rose

Agenus honouring the Mexican brothers Romulo (1872-1946) and Numa Escobar (1874-1949), founders of the Escuela Particular de Agricultura in 1906, in Ciudad Juarez, Chihuahua, Mexico (see portraits above, public domain).
A genus of low-growing, small solitary or caespitose plants, with stems globose or cylindrical, not ribbed. Spines usually short, finely aciculate, covering the epidermis of the plant.
Flowers diurnal, self-sterile, apical or appearing near the apex, with a short floral tube, the outer segments of the perianth ciliate, pink, magenta, purple or more rarely yellowish, pollinated among others by bees (Halictidae). Fruits globose or elongated, usually red, but also pink or green. Seeds subglobose, dull, light brown to blackish brown, foveolate (dotted with holes).
The genus Escobaria grows on a variety of soils, mostly rocky or alluvial, among grasses, in rock crevices, in grasslands, on hilly reliefs, rocky slopes with low xerophytic vegetation, limestone terraces and outcrops, in mountains, in the shade of shrubs or in full sun, from 800 m up to 2650 m in altitude, together with other cacti.
Canada (Alberta, Manitoba, Saskatchewan), Mexico (Chihuahua, Coahuila, Durango, Nuevo Leon, Sonora), USA (Arizona, California, Colorado, Idaho, Iowa, Kansas, Montana, Minnesota, Nebraska, Nevada, North Dakota, New Mexico, Oklahoma, Oregon, South Dakota, Texas, Utah, Wyoming).

Currently 9 recognised species (+ 3 subspecies):
– Escobaria albicolumnaria Hester 1941
– Escobaria alversonii (J.M.Coult.) N.P.Taylor 1997
– Escobaria chihuahuensis* Britton & Rose 1923 (possibly wrongly placed)
– Escobaria chihuahuensis subsp. henricksonii (Glass & Foster) N.P.Taylor 1998 (possibly wrongly placed)
– Escobaria desertii (Engelm.) Buxb. 1951 [ex Coryphantha chlorantha (Engelm.) Br.& R.]
– Escobaria hesteri* (Y.Wright) Buxb. 1951
– Escobaria laredoi* (Glass & Foster) N.P.Taylor 1979 (possibly wrongly placed)
– Escobaria sneedii Britton & Rose 1923
– Escobaria sneedii subsp. leei (Boed.) D.R.Hunt 1997
– Escobaria sneedii subsp. orcuttii (Boed.) Luethy 1999
– Escobaria tuberculosa* (Engelm.) Britton & Rose 1923
– Escobaria vivipara* (Nutt.) Buxb. 1951

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)