Acharagma is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of two small cacti

Cactus

A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 from northern Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

.

These cacti are usually solitary but sometimes occur in small clusters. The globose stems tend to be about 3-7 cm in diameter. The ribs have tubercles, with ungrooved areole

Areole

Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...

s. The flowers are at the stem tips, and range from cream to pink and yellow.

The genus is of relatively recent creation, the species originally being described as part of Escobaria

Escobaria

Escobaria or foxtail cactus is a genus of low-growing cacti that range from the southernmost parts of central and western Canada through northern Mexico, with one species in Cuba...

, although recognized as a separate section by Nigel Taylor in 1983, and raised to a genus by Charles Glass

Charles Glass

Charles Glass is an American author, journalist, and broadcaster specializing in the Middle East. He writes regularly for The Spectator, was ABC News chief Middle East correspondent from 1983–93, and has worked as a correspondent for Newsweek and The Observer...

in 1998.