Acharagma (N.P. Taylor) A.D. Zimmerman ex Glass, Guía Identif. Cact. Amenazadas México 1:  [AC/AG], 1998. Escobaria sect. Acharagma N. P. Taylor, Kakteen. Sukk., 34: 185, 1983. Escobaria subgenus Primibaria V. John & Riha, Kaktusy (Brno) 17: 41, 1981.
Type: Acharagma roseana (Boed.) E.F. Anderson (=Echinocactus roseanus Boed.)
Etymology: Greek: a= not, and charagmo= grooved
Plants usually solitary, sometimes forming small cespitose clusters. Roots tuberous, succulent, soft and more or less fragile. Stems globose to short cylindrical, 3-7 cm in diameter, lacking extra-floral nectar glands. Ribs weakly defined, forming well-developed tubercles. Areoles borne on the rib-tubercle tips, lacking adaxial grooves. Spines present, usually dense, 12-31 per areole; central spines 2-6, similar to radial spines, largest 0.15-0.35 mm in diameter brittle; radial spines projecting slightly, not appressed, upper ones, 8-15(-20) mm long, lower ones (5.5-)7-10 mm long,. Flowers borne at the upper margins of the spine clusters, at the stem apex, 18-24 mm long, 15-18 mm in diameter, usually not opening widely; floral tubes short; tepals not ciliate; inner tepals 8-13), pale yellowish or cream-colored, with or without reddish, dull brownish pink to maroon midveins, 10-11.5(-13) mm long, 2.5-3.5(-4.5) mm wide; outer tepals entire, minutely aristate; nectar chamber funnelform, 0.5-0.75 mm long; stigma lobes 4-6, white to yellow. Fruits clavate, fusiform or obovoid, green, pink, purplish-bronze, (7-)10-20 mm long and 3-5 mm in diameter, succulent and juicy, indehiscent; floral remnant persistent; bracts of pericarpel 0-3, linear, aristate; white trichomes, <1 mm long in axils of bracts, ±concealed. Seeds reddish brown to black, 1-1.5 mm long, comma-shaped or reniform, seed coat cells concave. Two species endemic to Coahuila and Nuevo Leon, Mexico.
1. Tepals pink or cream with dark reddish-pink midveins; spines yellow; plants branched; stems (1.5-)3-5 cm thick. . . . . . . . . . . . . . . . . . Acharagma roseana
1’. Tepals yellow or yellowish-red; plant usually unbranched; spines purplish gray to orange-tan; stem 5-7 cm thick. . . . . . . . . . . . . . . . . . Acharagma aguirreanum
Figure 1 . Acharagma aguirreanum in cultivation, bearing brownish spines (A), and in flower (B). Acharagma roseana subsp. galeanensis in cultivation, bearing yellowish-white spines and cream-yellow flowers (C and D). Acharagma roseana subsp. roseana in cultivation, bearing whitish spines, and pink flowers (E and F).
Figure 3 . Seed coat micromorphology in Acharagma aguirreanum: upper panel showing cells on the dorsal side; lower panel showing cells adjacent to the hylem-micropyle region. The scale bar is 20 microns.
Figure 4 . Scanning electron micrograph of the pollen of Acharagma aguirreanum. The scale bar of the top image is 10 microns in length; in the lower image it is 1.0 micron.