Key to Cactaceae
View taxon page for Cactaceae
Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.
1. Stem regularly segmented;
areoles with glochids;
seeds tightly encased within bone-like
aril, ± white when dry
2. Stem
segments flat,
tubercles 0 to ± developed;
spine surface not separating
..... OPUNTIA 2' Stem segments
cylindric Elongate, with parallel sides and, at any point, round in transverse section.
to club-like, generally tubercled; spine surface sheath-like, generally separating and late-deciduous
3. Spines not flat; spine
sheath A surrounding or partially surrounding, often tubular structure or part of a structure, such as a leaf base in Apiaceae or Poaceae.
0 or fully separating; mature plant generally 0.3–4 m
..... CYLINDROPUNTIA 3' Major
spines flat; spine sheath separating only from tip; mature plant generally < 0.25 m
..... GRUSONIA 1' Stem not regularly segmented; glochids 0; dry seeds generally black to ± red-brown, lacking a ± white bone-like aril
4. Largest spines with
transverse ridges; spines generally 2–5 mm diam near base, rigid
5. Ovary, generally
stem tip densely woolly, obscuring
epidermis,
ovary scales tapered Gradually (not abruptly) narrower or smaller at base or tip.
to sharp tips
..... ECHINOCACTUS 5' Ovary, stem tip
glabrous, only areoles woolly, ovary scales generally rounded
..... FEROCACTUS 4' Largest spines smooth or longitudinally ridged; spines generally < 2 mm diam near base, rigid or not, thin, flexible if > 2 mm wide
6. Stem
ribs 0 or inconspicuous, tubercles prominent
7. Spines all straight to ± curved; stem tubercles with woolly,
adaxial groove connecting spine cluster to
axillary Pertaining to or within an axil, especially a leaf axil.
flower
areole ..... ESCOBARIA 7' Some spines in each areole generally hook-shaped; stem tubercles not adaxially grooved
..... MAMMILLARIA 6' Stem ribs prominent, tubercles ± 0 or prominent on ribs
8. Stem > 30 cm diam, branched but generally not in
basal At or near the base of a plant or plant part. Especially said of leaves clustered near the ground or of a placenta confined to the base of an ovary.
1.5–2 m;
perianth generally white
..... CARNEGIEA 8' Stem < 15 cm diam, not branched, or branched in basal 1.5 m; perianth variously colored, but generally not white
9' Stem length < 6 × diam; fruit not persistent when empty, spineless or spines
deciduous; inland
10. Flowers
lateral; ovary minutely scaly, spiny, spines deciduous in clusters; stem soft-fleshy, branches 1–500
..... ECHINOCEREUS 10' Flowers at stem tip or nearly so; ovary scaly, spineless; stem ± hard, branches 0–few (more if stem damaged)
..... SCLEROCACTUS
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