Flora of North America species comparison

obconic taproots;

secondary roots diffuse.

upper portion of primary root somewhat thickened and succulent proximally, otherwise fibrous.

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.

flat-topped or spheric, 4–8 × 4–8 cm, ± flaccid;

tubercles 6–24 mm;

axils appearing naked;

cortex and pith mucilaginous;

latex absent.

(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.

9–31(–34) per areole, white, usually tipped brown;

radial spines 8–30 per areole, in 1 series, glabrous (puberulent in first year flowering plants);

lateral spines bristlelike, 7–11 mm, stiff, longest and thickest of spines;

adaxial spines often darker;

central spines 1–4(–7) per areole, porrect or strongly projecting, 1 or all hooked, (5–)12–14(–21) 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.

2.5–3.5(–5.2) × 2.2–4.5(–7.5) cm;

outer tepal margins conspicuously fringed;

inner tepals rose-pink or magenta [white], margins often paler;

stigma lobes yellow or pale green (rarely reddish).

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

floral remnant weakly persistent.

green or dull purple, spheric to ovoid or obovoid, (9–)13–20(–28) × (6–)7–1.9(–26) mm, juicy throughout;

floral remnant 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.

black, 1.3–1.5 mm, pitted;

testa hard, anticlinal cell walls straight (not undulate);

interstices conspicuously narrower than pit diameters;

pits bowl-shaped.

= 22.

= 22.