Flora of North America species comparison

obconic taproots;

secondary roots diffuse.

top-shaped, flat-topped (aerial part sometimes hemispheric in old age or in dense subtropical vegetation), protruding above ground 0–2 × (4–)7.5–15 cm, firm;

tubercles 9–15(–20) × 3–7 mm;

axils with short wool, bristles absent;

cortex and pith not mucilaginous;

latex abundant in healthy tissue throughout cortex of stem, tubercles, and sometimes flower receptacle, sticky, white.

(8–)10–18(–27) per areole, usually brownish, darker at tip, glabrous;

radial spines (8–)10–22(–26) per areole, white to white-and-brown or brown, needlelike, 6–15(–16) mm, stiff, abaxial spines longest;

central spines (0–)1(–4) per areole, porrect or ascending, not hooked, (0.5–)2–8 × 0.15–0.45 mm;

subcentral spines 0.

1.9–3.8 × 1.5–3 cm;

outermost tepal margins entire;

inner tepals white, greenish or cream to pale pink, with tan, pink, greenish, or brownish midstripes, 11–19 × 2–2.5 mm;

stigma lobes externally green, internally green or red (or pink), 2.5–3 mm.

brilliant red: scarlet, carmine, or crimson, obovoid to clavate, 10–35(–40) × 5–8 mm, juicy only in fruit walls;

floral remnant weakly persistent.

reddish brown, sometimes yellowish when fresh, 1–1.2 mm, deeply pitted;

testa thin, relatively flexible;

anticlinal cell walls sinuate, interstices narrower than pit diameters;

pits cavernous or deeply concave.

= 22.