CACTACEAE

CACTUS FAMILY

Edward F. Anderson (except Opuntia)

Perennial, shrub, tree, generally fleshy
Stem cylindric, spheric, or flat; surface smooth, tubercled, or ribbed (fluted); nodal areoles bear flowers, generally bear spines from center ("central spines") and margin ("radial spines") (Opuntia areoles bear small, barbed, deciduous bristles sometimes called glochids, generally also bear spines)
Leaf generally 0
Flower generally solitary, bisexual, sessile, ± radial; perianth parts generally many, grading from scale-like to petal-like; stamens many; ovary appearing inferior, ± submerged in stem, so generally with areoles on surface, style 1, stigma lobes generally many
Fruit generally fleshy, generally indehiscent, spiny, scaly, or smooth
Seeds many
Genera in family: 93 genera, ± 2000 species: especially Am deserts; many cultivated
Etymology: (Greek: thorny plant)
Reference: [Benson 1982 Cacti of US & Can; Hunt & Taylor eds 1990 Bradleya 8:85–107]

OPUNTIA

PRICKLY-PEAR, CHOLLA

Bruce D. Parfitt and Marc A. Baker

Shrubs, trees; roots fibrous
Stem generally erect, < 12 m; segments flat to cylindric, generally firmly attached; tubercles generally elongate along stem; ribs sometimes present; spines 0–many, sometimes flat, tip smooth or barbed, epidermis persistent or separating as a papery sheath; small, barbed deciduous bristles generally many
Leaf small, conic, fleshy, deciduous, obvious on young stems and ovaries
Fruit juicy, fleshy or dry; wall thick, bearing areoles
Seed dark brown, encased in a bony, whitish aril
Species in genus: 200 species: Am; O. ficus-indica cultivated for food, others for ornamental
Etymology: (Possibly from Papago Indian name ("opun") for this food plant; or named for a spiny plant of Opus, Greece)
Spines smaller, fewer in shade forms; when yellow, blacken with age. Hybridization common within subgenera.

Native

O. X munzii C.B. Wolf

MUNZ'S CHOLLA

Stem < 2.4 m; trunk 1; branches several; segments cylindric, terminal easily detached, generally < 10 cm, 3–5 cm diam; tubercle 10–16 mm, 3–4 mm high; spines 9–16, < 4 cm, pale red-brown, sheath yellow-brown
Flower: inner perianth 1.5–2 cm, yellow-green to red-brown; filaments pale green
Fruit 2.5–3.5 cm, dry, low tubercles, often with deciduous spines
Seed 3 mm
Chromosomes: 2n=22
Ecology: Gravelly or sandy soils of washes, canyon walls
Elevation: 150–600 m.
Bioregional distribution: Sonoran Desert (Chocolate, Chuckwalla mtns, Imperial, Riverside cos.)
Flowering time: May
Probable hybrid of O. bigelovii and O. echinocarpa (see O. X fosbergii). Most localities ± inaccessible
Recent taxonomic note: Cylindropuntia munzii (C.B. Wolf) Backeb. (pro hybr.)
Horticultural information: In cultivation.