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Published In: Genera Plantarum 310. 1789. (4 Aug 1789) (Gen. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 8/10/2009)


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CACTACEAE (Cactus Family)

(Benson, 1982; Anderson, 2001)

Ninety-three to 125 genera, 1,400–1,850 species, North America to South America, Caribbean Islands; 1 species in Africa, Madagascar.

The morphology of cactus plants requires some explanation. Except for the relatively primitive genus Pereskia Mill., which includes more or less normal-looking spiny shrubs and trees with well-developed leaves, in cacti the stems have become modified and thickened to serve in photosynthesis and water storage, whereas the leaves are essentially absent or very short-lived. There is a bewildering diversity of stem shapes, sizes, surface textures, and branching patterns in the family. The spines of cacti are produced on areoles, which can be thought of as extremely short, highly modified branches. Spines actually develop from the axillary buds associated with the numerous closely spaced nodes of the areole and often appear to have a more or less radial distribution on the areole. Flowers also are produced in association with areoles and developmentally are thus considered to be axillary and solitary (except in Pereskia). Most species produce flowers with numerous perianth parts that grade continuously from sepaloid to petaloid morphology along the densely spiraled series and thus are referred to as tepals. Taxonomically, the family is considered to represent a morphologically specialized offshoot of the Portulacaceae (Hershkovitz and Zimmer, 1997; Applequist and Wallace, 2001) and to have experienced an explosive radiation of species in the New World, with the result that many of the species are difficult to distinguish from others within a given complex. This has led to great controversy as to species numbers and delimitation in most of the larger genera (generic delimitation has been equally contentious). In an effort to stabilize the nomenclature and taxonomy of the family, since 1984 an International Cactaceae Systematics Group of specialists has worked to produce a consensus classification and checklist (Hunt, 1999) for use by horticulturalists, conservation officers, and others interested in the family.

With their unusual stems and bright flowers, cacti are popular both among amateur enthusiasts and botanists. In fact, there is a huge horticultural market for cacti, which also have economic importance as landscape plants in dry and seasonally dry regions of the United States and other countries. Overcollection from the wild for horticultural purposes has led to the endangerment of numerous species, thus international trade in most cacti is closely regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Some species of cacti, particularly members of Opuntia and related genera, also are cultivated for their edible fruits and stems and as hosts for homopteran cochineal insects (Dactylopius spp.), which produce a beautiful red dye. Other genera, particularly peyote (Lophophora williamsii (Lam. ex Salm-Dyck) J.M. Coult.), have been cultivated and/or wild-harvested for their hallucinogenic properties. The wood of various cacti sometimes is used in handicrafts. Cactus spines can cause damage to the legs, feet, and mouthparts of livestock, and some cacti have been considered pest plants in pastures. This is especially true in Australia, where imported Opuntia species rendered millions of acres of rangeland unfit for livestock and other uses until biological controls involving stem-boring larvae of the South American moth genus Cactoblastus proved effective.

In addition to the numerous species cultivated in homes, greenhouses, and conservatories, several nonnative cacti are cold-hardy in Missouri’s climate and are cultivated outdoors as specimen plants in well-drained soils. These generally have not escaped into the wild, but they occasionally persist at old homesites. The best example of this is a tree cholla, Cylindropuntia imbricata (Haw.) F.M. Knuth (Opuntia imbricata (Haw.) DC., O. arborescens Engelm.), which is native from Colorado to Kansas south to Texas and Mexico. A single individual of this species was located in 1998 by an amateur botanist, T. Owens, in Laclede County growing on a dry ridgetop overlooking the Niangua River. This species has cylindrical stems to 2 m tall and 3 cm in diameter that are covered with coarse, elongate tubercles and dense clusters of spines. The stems are jointed every 5–35 cm and have whorled branches. The flowers have bright pink to reddish purple tepals to 5 cm long, and the broadly obovoid fruits are spineless and more or less yellow at maturity. This species eventually may need to be added to the roster of the state’s flora and should be searched for, especially in the Unglaciated Plains Division.

Beginning with an unsubstantiated listing from Pulaski County (Palmer and Steyermark, 1935), there also have been persistent anecdotal reports (mostly from western Missouri) of another regionally native cactus species, Escobaria missouriensis (Sweet) D.R. Hunt (Mammillaria missouriensis Sweet, Coryphantha missouriensis (Sweet) Britton & Rose; Neobesseya missouriensis (Sweet) Britton & Rose, Neomammillaria missouriensis (Sweet) Britton & Rose, Neomammillaria similis (Engelm.) Britton & Rose), which is known by various common names, including ball cactus, beehive cactus, cream cactus, and Missouri pincushion cactus. Its distributional range stretches from Idaho to Arizona east to North Dakota, Kansas, and Texas (also adjacent Mexico). Steyermark (1963) excluded it from the Missouri flora, but searches of thin-soil areas of prairies, glades, and bluff tops may result in its eventual documentation from the state. Escobaria missouriensis produces small, globose to broadly obovoid stems, these 2–5 cm long, solitary or forming small, clustered mounds, and covered with nipplelike tubercles tipped with a dense cluster of short, straight spines. The flowers have narrow tepals 1–2 cm long that are cream-colored to light yellow or greenish yellow, often reddish- or pinkish-tinged toward the base. The globose to obovoid fruits are 1–2 cm long, spineless, and bright red at maturity.


Lower Taxa
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