Disocactus

The members of the tribe Hylocereeae have resulted in much controversy, partly because many taxa, including genera, were proposed with little real knowledge of the plants in the wild. Field and laboratory studies have now clarified the situation somewhat, though there is still disagreement. Myron Kimnach (1961,1979,1993) has conducted extensive research on Disocactus and related genera, defining boundaries between genera somewhat differently than those accepted by Wilhelm Barthlott (1991a) and the International Cactaceae

Systematics Group. Kimnach included Pseudorhipsalis in Disocactus but recognized Aporocactus, Heliocereus, and No-palxochia as separate genera. Barthlott, on the other hand, separated Pseudorhipsalis as a distinct genus but included Aporocactus, Heliocereus, and Nopalxochia in Disocactus. Thus two well-qualified scientists look at the same plants and data yet come to different conclusions. Barthlott (1991a) commented, however, "no one disagrees... that the taxa are closely related," especially considering how easily they hybridize. Recognizing the excellent work of both researchers, I accept Disocactus as defined by Barthlott and the International Cactaceae Systematics Group, primarily because I use the group's classification system for consistency here.

Disocactus (type, Cereus biformis = D. biformis) was described in 1845 by John Lindley, who derived the name from the Greek dis, twice, thus twice cactus, referring to the two series of perianth segments, equal in size. Nathaniel Britton and Joseph Rose (1919-1923,4:201-203) accepted Disocactus, adding another species, D. eichlamii. The amplified genus of Barthlott (1991a) has 16 species, mostly occurring in Central American rain forests, and is subdivided into five subgenera, Ackermannia, Aporocactus, Disocactus, Nopalxochia, and Wittia.

Disocactus contains many of the so-called orchid cacti or epiphyllums. Several of the most popular forms are hybrids; see under D. speciosus. Flowers of Disocactus are large, often brightly colored, and solitary, open during the day in spring or early summer.

Disocactus Lindley 1845 Aporocactus Lemaire 1860 Wittia K. Schumann 1903 Heliocereus (A. Berger) Britton & Rose 1909 Chiapasia Britton & Rose 1923 Nopalxochia Britton & Rose 1923 Bonifazia Standley & Steyermark 1944 Lobeira Alexander 1944 Pseudonopalxochia Backeberg 1958 Wittiocactus Rauschert 1982

Subfamily Cactoideae, tribe Hylocereeae. Plants epiphytic or litho-phytic shrubs. Stems ribbed or flattened or leaflike, with the main stems often round in cross section basally but flattened above. Lateral stems flattened. Areoles often proliferous. Spines bristly or absent. Flowers usually borne singly, large, diverse in size and shape, open during the day, funnelform ortubular, sometimes bilaterally symmetrical, rarely rotate, brightly colored, red, pink orange, pale yellow, or white; stamens in two series, upperone sometimes forminga distinct throat circle. Fruits berrylike, almost naked or with a few small scales. Distribution: mainly Central America but also into the Caribbean and northern South America.

Disocactus ackermannii (Haworth) Barthlott 1991 Epiphyllum ackermannii Haworth 1829, Cactus ackermannii (Haworth) Undley 1830, Cereus ackermannii (Haworth) Otto 1837, Phyllocac-tus ackermannii (Haworth) Salm-Dyck 1842, Nopaixochia actcer-mannii (Haworth) F. M. Knuth 1935 Phyllocactus weingartii A. Berger 1920 Nopaixochia conzattianum t. MacDougall 1947, Pseudonopalxochia conzattianum (t. MacDougall) Backeberg 1959, N. ackermannii var. conzattianum (t. MacDougall) Klmnach 1981, Disocactus acker-mannii var. conzattianum (T. MacDougall) Barthlott 1991

Plants arching, branching basally, to nearly 1 m (3.3 ft) long, without long stems. Stem bases round in cross section and

10-18 cm (3.9-7.1 in) long; flattened portions 10-75 cm (3.9-30 in) long, 5-7 cm (2-2.8 in) wide, with wavy margins, brownish, becoming dark green, somewhat leaflike. Flowers curved funnelform, scarlet with greenish throats,

11-14 cm (4.3-5.5 in) long. Fruits ovoid to oblong, green to brownish red, 4 cm (1.6 in) long, 2-2.5 cm (0.8-1 in) in diameter. Distribution: Veracruz and Oaxaca, Mexico.

Disocactus ackermannii is quite variable and two varieties are recognized. Variety ackermannii has flattened stem portions 35-75 cm (14-30 in) long, and perianth segments 7-10 cm (2.8-3.9 in) long; it occurs in both Veracruz and Oaxaca. Variety conzattianum has flattened stem portions 10-50 cm (3.9-20 in) long, and perianth segments only 4-6 cm (1.62.4 in) long; it occurs only in Oaxaca.

Disocactus amazonicus (K. Schumann) D. R. Hunt 1982 Wittia amazonica K. Schumann 1903, Wittiocactus amazonicus

(K. Schumann) Rauschert 1982 Wittia panamensis Britton & Rose 1913, Wittiocactus panamensis (Britton & Rose) Rauschert 1982

Plants freely branching, shrublike with erect, then pendent branches. Stems with stalklike bases, lance shaped, leaflike, spineless, with pronounced midribs, strongly notched marginally, green, 15-40 cm (5.9-16 in) long, 5-9 cm (2-3.5 in) wide. Flowers erect, narrowly cylindrical, carmine with purplish blue tips and white inner perianth parts, 3-4 cm (1.21.6 in) long. Fruits off-white, to 1.5 cm (0.6 in) long. Distribution: Costa Rica, Panama, Brazil, Colombia, Venezuela, Ecuador, and Peru.

Disocactus aurantiacus (Kimnach) Barthlott 1991 Heliocereus aurantiacus Kimnach 1974

Plants pendent, branching basally, to 3 m (9.8 ft) or more long. Stems erect when young, then pendent, two- to five-angled to flattened, margins toothed and lobed, to 1 m (3.3 ft) long, 1-2 cm (0.4-0.8 in) wide when angled, 1.5-3 cm (0.6-1.2 in) wide when flattened. Spines absent or as many as 30, hairlike, cream colored, to 15 mm (0.6 in) long. Flowers borne singly on the apical half of the stem, funnelform, up-curving, light to medium orange, tinged with magenta, 12.515.5 cm (4.9-6.1 in) long. Fruits ellipsoidal,yellowish green

Disocactus amazonicus, photograph by Urs Disocactus biformis, photograph by Wilhelm Disocactus eichlamii, photograph by Wilhelm

Eggli Barthlott Barthlott

Disocactus amazonicus, photograph by Urs Disocactus biformis, photograph by Wilhelm Disocactus eichlamii, photograph by Wilhelm

Eggli Barthlott Barthlott tinged with pink, 7 cm (2.8 in) long. Distribution: Mexico, Honduras, and Nicaragua.

Disocactus biformis (Lindley) Lindley 1845 Cereus biformis Lindley 1843, Phyllocactus biformis (Lindley) Labouret 1853, Epiphyllum biforme (Lindley) G. Don 1855

Plants freely branching from a fairly long cylindrical stem. Stems flat, leaflike, to 20 cm (7.9 in) long, 1-2 cm (0.4-0.8 in) wide, with toothed margins. Areoles small, spineless. Flowers borne laterally and singly, curved upward, funnelform, reddish to magenta, 5-6 cm (2-2.4 in) long. Fruits ovoid, reddish purple, 1.5 cm (0.6 in) long. Distribution: Guatemala and Honduras.

Disocactus cinnabarinus (Eichlam ex Weingart) Barthlott 1991

Cereus cinnabarinus Eichlam ex Weingart 1910, Heiiocereus cinnabarinus (Eichlam ex Weingart) Britton &Rose 1920 Heiiocereus heterodoxus Standley & Steyermark 1944

Plants often creeping or clambering. Stems three-angled, dark green, very slender, 38-60 cm (15-24 in) long, 2-3 cm (0.8-1.2 in) wide. Areoles prominent, with as many as 10 bristle-like, yellowish brown spines to 8 mm (0.3 in) long. Flowers wide funnelform, slightly curved, greenish red outside with glossy brownish red inner perianth parts, to 15 cm (5.9 in) long, 8-9 cm (3.1-3.5 in) in diameter. Distribution: Mexico, Guatemala, Honduras, and El Salvador.

Disocactus flagelliformis, photograph by Charles Glass

Disocactus eichlamii (Weingart) Britton &Rose 1913 Phyllocactus eichlamii Weingart 1911, Epiphyllum eichlamii (Weingart) L. O.Williams 1962

Plants with cylindrical, slender stems, erect at first, becoming arching or pendent, producing numerous branches. Primary stems flattened or three-angled, from bases round in cross section. Secondary stems branching from the apical halves of the primary stems, rounded basally, flattened apically, slightly fleshy, with wavy margins, to 40 cm (16 in) long, 1.55 cm (0.6-2 in) wide. Areoles spineless. Flowers borne in succession along the lengths of the flattened stems, solitary or in clusters of as many as five, narrowly tubular funnelform, carmine red, 6-8 cm (2.4-3.1 in) long, with exserted stamens and styles. Fruits globose with apical projections, red, 9-14 mm (0.4-0.6 in) in diameter. Distribution: Guatemala.

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Responses

  • Vito
    How to seperate epiphyllum ackermannii from disocactus speciosus?
    6 years ago

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