Mamillaria

Mammillaria is one of the largest genera in the cactus family (Cactaceae), with currently 200 known species and varieties recognized. Most of the mammillarias are native to Mexico, but some come from the southwest United States, the Caribbean, Colombia, Venezuela, Guatemala and Honduras. The common name 'pincushion cactus' refers to this and the closely related genus Escobaria. The first species was described by Carl Linnaeus as Cactus mammillaris in 1753, deriving its name from Latin mammilla, 'nipple', referring to the tubercles that are among the distinctive features of the genus. Numerous species are commonly known as globe cactus, nipple cactus, fishhook cactus or pincushion cactus though such terms may also be used for related taxa, particularly Escobaria. The distinctive feature of the genus is the possession of an areole split into two clearly separated parts, one occurring at the apex of the tubercle, the other at its base. The apex part is spine bearing, and the base part is always spineless, but usually bears some bristles or wool. The base part of the areole bears the flowers and fruits, and is a branching point. The apex part of the areole does not carry flowers, but in certain conditions can function as a branching point as well. The plants are usually small, globose to elongated, the stems from 1 cm to 20 cm in diameter and from 1 cm to 40 cm tall, clearly tuberculate, solitary to clumping forming mounds of up to 100 heads and with radial symmetry. Tubercles can be conical, cylindrical, pyramidal or round. The roots are fibrous, fleshy or tuberous. The flowers are funnel-shaped and range from 7 mm to 40 mm and more in length and in diameter, from white and greenish to yellow, pink and red in colour, often with a darker mid-stripe; the reddish hues are due to betalain pigments as usual for Caryophyllales. The fruit is berry-like, club-shaped or elongated, usually red but sometimes white, magenta, yellow or green. Some species have the fruit embedded into the plant body. The seeds are black or brown, from 1 to 3 mm in size. The genus Mammillaria in the family Cactaceae was proposed by Adrian Hardy Haworth in 1812 and officially recognized by the International Botanical Congress of 1930. Initial spellings varied by authors but Mammillaria is now recognized as the accepted spelling. Mammillaria is a large and diverse genus with many species often exhibiting variations due to the nature of terrain, weather, soil and other ecological factors. As a result, subdivisions within the species has been rather inconsistent over time. Initially, some investigators were more inclined to consider each variation as a unique species, although as time went on, creating confusion and long synonymy-lists for some of the species. Over time, new investigators began grouping closely related forms under the same name to attempt to more accurately define the species. Several systems for classification began to emerged. The first of note, created by Schumann and modified by Berger, divided the species into ten named groups. However, the criteria for these divisions was somewhat indefinite and flexible. In the early 1923, cactologists Nathaniel Lord Britton and Joseph Nelson Rose developed the Britton & Rose system which arranged the classification characteristics in a system of keys with tangible separation factors, resulting in a much more workable system of identification. Later classification was performed by the cactus specialists Hunt, Reppenhagen and Luthy, with much work focusing on researching the meanings and value of the original plant descriptions, synchronizing them with modern taxonomic requirements and studying the morphology of plants and seeds, as well as ecological aspects of the genus. These works helped to expand the understanding of Mammillaria taxa.