''Calymmanthium'' is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of primitive tree-like

cacti A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...

from northern

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

. The only species is ''Calymmanthium substerile'' (also known as ''C. fertile''). It belongs to the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English language, English is in the discipline of anthropology. This definition is contested, in p ...

Lymanbensonieae. Calymmanthium is absolutely unique among flowering plants in the mode of its floral development. The young flower is completely encased within the plant's stem until it is fully developed, at which time a crack develops in the stem, allowing pollinators access. ''Diploperianthium''

F.Ritter Friedrich Ritter (9 May 1898 – 9 April 1989) was a German Botany, botanist who collected and described many species of cacti. ''Ritterocereus'' is named in his honour. References

1898 births 1989 deaths {{botanist-stub ...

(nom. inval.) has been brought into

synonymy A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

with this genus.

References

Cactoideae Cactoideae genera Cacti of South America Endemic flora of Peru Monotypic Cactaceae genera {{Cactus-stub