Commemorating the Mexican brothers Romulo and Numa Escobar of the early 20th century.
Body solitary to clustering, flattened spherical to cylindrical. Tubercles with or without a groove on the upper surface. Areoles at tip of tubercles, elongated and with straight spines but nectar-secreting glands absent. Flowers relatively small, mostly in the tubercle axils, outer perianth segment margins fringed. Pericarpel naked. Fruit fleshy, green pink or red, without structures except possibly a few scales at the tip.
A difficult genus with accurate identification of species requiring details of stigma lobes, fruits and seeds.
Similar to Mammillaria but the areoles without distinct spiny and flowering areas, and the flowers generally arising near the body apex; outer perianth segments often fringed. The grooved tubercles are similar to those of Coryphantha.
About 16 species from N Mexico and SW USA, S Canada and Cuba.
Taylor (1986).
The key should be used as a guide to commonly grown species only.
Species occasionally available include: E. minima (Baird) D.R. Hunt with pronounced symmetrically-arranged white radial spines closely pressed to the stem and magenta flowers; E. robbinsorum (Earle) D.R. Hunt from SE Arizona with pink to pale green flowers; E. sneedii Britton & Rose as var. sneedii Britton & Rose from Texas and var. leei (Boed.) D.R. Hunt from New Mexico.
Source: (1997). Cactaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.
