WikiBotanicals:Grusonia

Grusonia is a genus of opuntioid cacti (family Cactaceae), originating from the North American Deserts in Southwest United States and northern Mexico, including Baja California. Authors differ on precise boundaries of the genus, which has been included in Cylindropuntia.

Background
A low, much branched cactus, the branches terete, jointed, and ribbed; areoles borne on the tops of the ribs, very spiny, but all except the flowering ones without glochids, subtended by small deciduous leaves; corolla rotate, yellow; fruit baccate.

This was first described as a Cereus from specimens collected by Mrs. Anna B. Nickels in 1895, then as a new genus Grusonia, and lastly as an Opuntia. It clearly is not Cereus, but when growing might easily be mistaken by its habit for Echinocereus. The leaves, glochids, flowers, and fruit are those of Opuntia, but its ribbed stem is unlike that of any known species of that genus.

Species
G. aggeria (Big Bend pricklypear)

G. bradtiana Plains of Coahuila, Mexico. Forming dense, often impenetrable thickets 2 meters high or less, very spiny; steins light green, 4 to 7 cm. thick, with 8 to 10 low, longitudinal, somewhat tuberculate ribs; areoles 1 to 1.5 cm. apart, 3 to 5 mm. in diameter; leaves linear, fleshy, green, 8 mm. long, early deciduous; spines 15 to 25, yellowish brown when young, soon becoming white; acicular, terete or slightly compressed, 1 to 3 cm. long, not sheathed, some of the longer ones reflexed; wool white, turning brown, early disappearing; corolla rotate, opening in bright sunlight, 3 to 4 cm. broad; sepals ovate, acute, fleshy, petals bright yellow, spatulate, fringed; filaments brownish yellow; stigma-lobes 8, yellow; areoles of the ovary with long, yellow, weak spines, white wool, and yellow glochids; berry (according to Schumann) ellipsoid, deeply umbilicate; seeds not seen. Distributed in Coahuila, Mexico.

G. clavata (club cholla)

G. grahamii (Graham's pricklypear)

G. emoryi (devil cholla)

G. kunzei (devil's cholla)

G. parishii (matted cholla and Parish club cholla ) Mojave and Sonoran Deserts of the southwestern United States. grows in spreading mats along the sandy ground no more than about 20 centimeters tall. The segments are up to 9 centimeters long by 3 wide and is surfaced in fleshy tubercles bearing many spines each up to 5 centimeters in length. The flower is yellowish and the fruit is yellow and up to 8 centimeters long.

G. pulchella (sagebrush cholla)

G. schottii (Big Bend pricklypear)