Flora of North America species comparison

obconic taproots;

secondary roots diffuse.

short, 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.

flat-topped (in old age or under dense brush aerial portion of stem hemispheric), 10 × 8–10(–30) cm, firm;

tubercles 8–17 × 4–11 mm;

axils bearing (at least seasonally) woolly tufts, wool 3–5 mm, 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.

(6–)7–8(–10) per areole, white, reddish brown, gray, or yellowish, glabrous;

radial spines (5–)6–7(–9) per areole, largest spines reddish brown, gray, or yellowish, tips blackish or dark brown, needlelike, 6.5–13.5 × 0.3–0.6 mm, stiff;

central spines (0–)1 per areole, usually ascending and inconspicuous against radial spines, sometimes porrect, straight or slightly curved, largest spines (3–)5–12 × 0.3–0.7 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 × 1.9–3.5(–4.4) cm;

outermost tepal margins entire;

inner tepals white to pale pink, often with pink or lavender midstripes, 8–15 mm;

stigma lobes light green, 3–5 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.

purplish pink, clavate to obovoid, 20–32 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.

reddish brown, 1.1–1.2 mm; pitted;

testa leathery to hard, anticlinal cell walls strongly undulate, interstices much narrower than pit diam., pits deeply concave, elongate.

= 22.

= 22.