Acanthocalycium 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 cactus

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...

 consisting of three species from Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

. The taxon name comes from Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 akantha (meaning prickly) and kalyx (meaning buds), which refers to the spines on the floral tubes.

These plants are globose to elongate, with numerous ribs on the spiny stems

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

. Flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s range from white to pink to red and open during the day.

Taxonomy

Spinicalycium Fric

Alberto Vojtech Fric

Alberto Vojtěch Frič was a famous Czech botanist, ethnographer, writer and explorer. He undertook 8 voyages to America, discovered, described and catalogued many species of cactus....

(nom. inval.) has been brought into synonymy with this genus. Besides, the genus Acanthocalycium has been periodically included in the genus Echinopsis

Echinopsis

Echinopsis is a large genus of cacti native to South America, sometimes known as hedgehog cacti, sea-urchin cactus or Easter lily cactus. One small species, E. chamaecereus, is known as the peanut cactus. The 128 species range from large and treelike types to small globose cacti...

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