Xerophyte

Central Spines

1, curved slightly to fully hooked, (hooked only on relatively young plants), heavy, roughly cross-ribbed, annulate, thick, adaxially flat, 55-95(-130) long × 2.5-4 mm. in cross section.

Seeds

2 mm. in diameter, black.

Note

F. emoryi produce nectar in the nectaries at the top of the cactus that feed the ants that live around its base. In turn, the ants are very territorial and seem to protect the plants from other insects that might try to walk up the stem and damage the fresh, delicate cells at the growing apex or steal nectar or pollen from the flowers. This strategy is useful to not only to protect the plant from small herbivores but also to promote outcrossing pollination because the only bugs that can successfully visit the flowers without being attacked by the ants are flying pollinator insects like butterflies and bees that carry pollen from other individuals and other populations, in turn increasing the genetic diversity of the species.

Flowers

Reddish outside, brilliant red inside, 6-7.5 × 5-7.5 cm; inner tepals brilliant red [or occasionally yellow]; stigma lobes brilliant red.

Spines

6-10 per areole, reddish, reddish grey, or horn coloured, all robust and rigid, more than 1 mm diameter.

Ribs

(15-)21-32, shallowly notched immediately above each areole.

Stem

Erect, globular when young to a stout cylinder when older, 30-90(-250) tall × 30-60 (100) cm in diameter; tubercled when young later forming ribs.

Radial Spines

5 to 9 similar to central, spreading, not hooked, 2.5 to 5cm long.

Fruits

Persistent, oblong, scaled, 2,5-5cm long × 25-35 mm long in diameter with the dried remains of the flower atop, ± readily dehiscent through basal pore, bright yellow, 50, leathery or fleshy, locule dry, hollow except for seeds. Often the fruit are broken into and the seed eaten by birds or rodents.

Areoles

oval with brown wool, 2-2.5 cm apart.