Stenocactus

It is surprising that the small group of Mexican cacti known as Stenocactus is so poorly understood; there has even been controversy regarding the correct name of the genus. Stenocactus has long been popular with hobbyists and is relatively easy to propagate.

The problem of the correct name stems from the publication in 1841 of the name Echinofossulocactus by George Lawrence, who included 26 species, none designated as type and now considered to belong to at least five genera. Karl Schumann (1897-1898), almost certainly unaware of the fairly obscure publication by Lawrence, described the subgenus Stenocactus as part of the huge genus Echinocactus. Nathaniel Britton and Joseph Rose (1919-1923, 3: 109), however, were aware of Lawrence's name and resurrected it, choosing Echinofossulocactus coptonogonus as lectotype only because it was the first species alphabetically in Lawrence's list. The long name Echinofossulocactus was objected to by some people and two alternative names were proposed, Brit-tonrosia and Eofossus. David Hunt (1980a) undertook an analysis of the nomenclatural and taxonomic problems regarding this group of cacti. He found that Echinocactus helo-phorus (= E. platyacanthus) best fit Lawrence's characters and proposed it as the new lectotype of Echinofossulocactus, making Echinofossulocactus a synonym of Echinocactus, at first seeming to complicate matters. The Committee for Sperma-tophyta (1987) responded, however, rejecting conservation of the name Stenocactus, proposed by William Tjaden (1982).

Pictures And Names Cactus

Selenicereus wittii, photograph by Wilhelm Barthlott

In their several actions, the committee voted that Echino-fossulocactus was typified as proposed by Hunt, making it a synonym of Echinocactus and freeing the name Stenocactus for the cacti treated here.

The name Stenocactus is derived from the Greek stenos, narrow, thus narrow cactus, referring to the many narrow ribs. The only relatively recent review of the cacti included in Stenocactus is that by Nigel Taylor (1979a). Keith Gardner (pers. comm.) has carried out extensive field studies of the genus, but results have not been published. Two vegetative characters tend to separate Stenocactus from closely related genera: the narrow, finlike ribs, and the presence of areoles with large spines above and small ones below. Taylor (1983a) pointed out reproductive structures that strongly suggest Stenocactus should be submerged into Ferocactus, a genus to which it is certainly closely related. However, the International Cactaceae Systematics Group decided to recognize Stenocactus as distinct with 10 species, the status of 3 uncertain (S. hastatus, S. rectispinus, S. sulfureus). The species of Stenocactus are extremely variable in their vegetative characters, which has led to the proposal of numerous species. Plants flower during the day in summer.

Stenocactus (K. Schumann) A. W. Hill 1933 Echinocactus subg. Stenocactus K. Schumann 1898 P/ptantfiocereusRiccobonol909,inpartand probably excludingthetype Echinofossulocactus in the sense of Britton & Rose 1922, not Lawrence

1841 (see Echinocactus) Brittonrosea Spegazzini 1923, not validly published Eofossus Orcutt 1926, not validly published

Subfamily Cactoideae, tribe Cacteae. Plants small, low growing, usually solitary, subglobose to short cylindrical. Ribs numerous, acute, thin, often wavy, sometimes forming tubercles when young. Areoles few on each rib, widely spaced. Spines straight or curved upward, never hooked, clearly differentiated into two series: upper series large, often daggerlike, lower series the radials. Flowers small, short fun-nelform to bell shaped, white with brownish or violet midveins; peri-carpels with scales; areoles of floral tubes and pericarpels naked. Fruits small, usually globose, pale green, slightly scaly, dry, dehiscing along one side. Seeds broadly oval, shiny blackish brown, with concave surface, 1.4 mm in diameter. Distribution: primarily the Chihua-huan Desert of northern and central Mexico.

Stenocactus coptonogonus (Lemaire) A. Berger ex A. W. Hill 1933

Echinocactus coptonogonus Lemaire 1838, Echinofossulocactus coptonogonus (Lemaire) Lawrence 1841, Ferocactus coptonogonus (Lemaire) N.P.Taylor 1980

Plants sometimes with several stems. Stems depressed globose, glaucous green, 5-10 cm (2-3.9 in) high, 8-11 cm (3.1-

4.3 in) in diameter. Ribs 10-15, stout, notched, with transverse grooves at the areoles, 5 mm or more in width. Areoles 2 cm (0.8 in) apart, elongated above the spines into the flower-bearing portion, sometimes with nectar glands, white wool soon deciduous. Spines 3-7, grayish white. Upper spines pointing vertically upward, broad, flattened, to 35 mm (1.4 in) long. Lateral pair pointing vertically upward, tetragonal. Lowermost pair, if present, short, slender, nearly round in cross section. Flowers white with violet midveins, to 3 cm (1.2 in) long and 4 cm (1.6 in) in diameter; floral tubes short. Distribution: Zacatecas, San Luis Potosi, Guanajuato, and Hidalgo, Mexico.

Stenocactus crispatus (A. P. de Candolle) A. Berger ex A. W. Hill 1933

Echinocactus crispatus A. P. de Candolle 1828, Echinofossulocactus crispatus (A. P. de Candolle) Lawrence 1841, Ferocactus crispatus (A. P. de Candolle) N. P. Taylor 1980 Echinocactus dichroacanthus Martius ex Pfeiffer 1837, Echinofossulocactus dichroacanthus (Martius ex Pfeiffer) Britton & Rose 1922, Stenocactus dichroacanthus (Martius ex Pfeiffer) A. Berger ex Backeberg 1935

Cactusexpert
Stenocactus coptonogonus, photograph by Charles Glass
Cactusexpert
Stenocactus crispatus

Echinocactus lanciferA. Dietrich 1839, Echinofossulocactus lancifer (A. Dietrich) Britton & Rose 1922, Stenocactus lancifer (A. Dietrich) A. Berger ex Backeberg & F. M. Knuth 1935 Echinocactus arrigens Link ex A. Dietrich 1840, Echinofossulocactus arrigens (Link ex A. Dietrich) Britton & Rose 1922, Stenocactus arrigens (Link & A. Dietrich) A. Berger 1929 Echinocactus lamellosus A. Dietrich 1847, Echinofossulocactus lamel-losus (A. Dietrich) Britton & Rose 1922, Stenocactus lamellosus (A. Dietrich) A. Berger 1929 Echinocactus flexispinus Salm-Dyck 1849, Echinofossulocactus flex-

ispinus (Salm-Dyck) Bravo 1969 Echinocactus violaciflorus Quehl 1912, Echinofossulocactus violaci-

florus (Quehl) Britton & Rose 1922 Echinofossulocactus confusus Britton & Rose 1922 Echinofossulocactus guerraianus Backeberg 1942 Echinofossulocactus kelleranus Krainz 1946 Echinofossulocactus multiareolatus Bravo 1960

Plants depressed globose, yellow-green to dark green, 8-12 cm (3.1-4.7 in) in diameter. Ribs 25-60, more or less folded and undulate, forming tubercles. Spine color and number variable, straight, rigid, unequal, white to yellow to brown. Central spines 1-4, 10-65 mm (0.4-2.6 in) long. Radial spines 2-10,4-28 mm (to 1.1 in) long. Flowers often borne in multiples from the stem tips, purple-violet, 2-4 cm (0.81.6 in) long, with distinct floral tubes covered with imbricate scales; perianth segments in two series. Distribution: northern and central Mexico from Zacatecas south into Puebla and Oaxaca. Stenocactus crispatus is extremely variable with one form intergrading into another, creating a tax-onomic nightmare.

Stenocactus hastatus (Hopffer ex K. Schumann) A. Berger 1929

Echinocactus hastatus Hopffer ex K. Schumann 1898, Echinofossulocactus hastatus (Hopffer ex K. Schumann) Britton & Rose 1922

Plants depressed globose, light green, to 10 cm (3.9 in) high and 12 cm (4.7 in) in diameter. Ribs 35, triangular in cross section, somewhat notched. Spines yellow to grayish. Central spine one, erect, to 4 cm (1.6 in) long. Radial spines 5-6, straight, some flattened, to 3 cm (1.2 in) long. Flowers large, yellowish white. Fruits not known. Distribution: Hidalgo, Mexico. Stenocactus hastatus is poorly known, not having been found recently in the wild. It may simply be a population of S. crispatus.

Continue reading here: Stenocactus multicostatus Hildmann ex K Schumann

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