Pelecyphora tuberculosa

Pelecyphora tuberculosa (syn. Escobaria tuberculosa), the corncob cactus, is a species of flowering plant in the family Cactaceae, native to the south-central United States, and northern Mexico.

Description
Escobaria tuberculosa grows singly or in groups and is very variable. The cylindrical to egg-shaped shoots reach heights of 5 to 12 centimeters with diameters of 2.5 to 7 centimeters. The warts, up to 10 millimeters long, become hard and persistent. The four to eight yellow, straight central spines have a pink or red tip and are 1 to 2 centimeters long. In the middle one of them is stronger. The approximately 20 to 30 yellow, white or gray marginal spines are straight and spread out. They are up to 1.2 centimeters long.

The fragrant flowers are pink and open wide. They are 2 to 3 centimeters long and reach the same diameter. The elongated fruits are usually red and 1.2 to 2 centimeters long.

Distribution
Escobaria tuberculosa is fairly widespread in the United States in the states of New Mexico and Texas, as well as in the Mexican states of Chihuahua, Durango, Coahuila and Nuevo León. It is only found growing on igneous rocks.

Taxonomy
The first description as Mammillaria tuberculosa by George Engelmann was published in 1856. The specific epithet tuberculosa comes from Latin, means 'humpy', and refers to the bumpy shoots of the species. Nathaniel Lord Britton and Joseph Nelson Rose placed the species in the genus Escobaria in 1923. Nomenclatural synonyms include Coryphantha tuberculosa (Engelm.) Orcutt (1922) and Coryphantha tuberculosa (Engelm.) A.Berger (1929).