Plants mostly erect (rarely decumbent or prostrate), branched or unbranched, deep-seated in substrate or not. Roots diffuse or taproots (adventitious from offsets in M. thornberi and M. prolifera). Stems unsegmented, green to gray-green, sometimes purplish under stress, spheric to cylindric or turbinate, often flat-topped, 1-15(-25) × 1.8-12(-20) cm, firm or flaccid; tubercles distinct, not confluent into ribs, pyramidal, conic, or cylindric, 3-25 × 2-9 mm; areoles of 2 kinds: vegetative areoles (spine clusters) at tips of tubercles; reproductive areoles in axils of tubercles, woolly, bristly, or naked; areolar glands absent; cortex and pith usually not mucilaginous, instead containing latex (absent in M. grahamii). Spines [2-]5-80(-90) per areole, of every color that cactus spines can be, hairlike, bristlelike, or needlelike, glabrous or plumose, (0.5-)2-25(-31) × 0.01-0.6 mm; radial spines (6-)10-80 per areole, straight to curved or crinkly bristles, (0.6-)3-25 mm; central spines 0-several (indefinitely numerous and intergrading with radial spines in M. lasiacantha), straight, curved, or hooked, terete. Flowers diurnal, in ring distant from stem apex (or nearly apical at anthesis forming a ring around new growth, subsequent apical growth displacing fruits even farther away from apex), in axils of tubercles, unconnected to spine clusters, funnelform, campanulate, or rotate, 0.9-4(-5.2) × 0.6-3.5(-7.5) cm; outer tepal margins entire or fringed; inner tepals yellow, white, rose-pink, magenta, or maroon, 4-30 × 1.5-8.5 mm; ovary lacking scales and spines; stigma lobes cream, yellow, red, pink, or brownish green, 0.3-8 mm. Fruits indehiscent, usually pink, bright red, or greenish, green and barrel-shaped when seeds mature, sometimes becoming colored and clavate or cylindric to ovoid, 5-30(-40) × (2-)4-9(-26) mm, usually juicy; scales and spines absent (or rudimentary); floral remnant persistent to quickly deciduous. Seeds black, brown, reddish, or yellowish (with tan, corky strophioles in M. tetrancistra), 0.8-1.5 × 0.6-1.4 mm, usually pitted or raised-reticulate (with additional wrinkling in M. tetrancistra) [impressed-reticulate M. candida of Mexico], often shiny; testa cells flat to concave, walls straight to sinuate. x = 11.
Home