The stems of Disocactus ackermannii consist of a short rounded base, about 10–18 cm (4–7 in) long, followed by longer flattened leaf-like portions, 10–75 cm (4–30 in) long and 5–7 cm (2–3 in) wide with wavy edges. The plant branches from the base and arches downwards, being altogether some 1 m (3 ft) long. The scarlet flowers have greenish throats and are funnel shaped, 11–15 cm (4.3–5.9 in) or even longer and up to 15 cm (5.9 in) across. The filaments are red but the base is usually greenish. The anthers are pale rose. The style are red. The stigma is purplish. Fertilized flowers are followed by green to brownish red fruits, 4 cm (1.6 in) long and 2–2.5 cm (0.8–1.0 in) wide.[2][4]
The species was originally named Epiphyllum ackermannii by Adrian Hardy Haworth in 1829. There are three sets of synonyms:[2]
Haworth's Epiphyllum ackermannii was successively transferred to Cactus ackermannii (1830), Cereus ackermannii (1837), Phyllocactus ackermannii (1842) and Nopalxochia ackermannii (1935) before the current Disocactus ackermannii (1991).
Phyllocactus weingartiiA.Berger is an independent synonym.
Nopalxochia conzattianum was named by Thomas Baillie MacDougall in 1947. It was successively transferred to Pseudonopalxochia conzattianum (1959) and Nopalxochia ackermannii var. conzattianum (1981) before the current Disocactus ackermannii var. conzattianum (1991).
Two varieties are currently recognized. D. a. var. ackermannii has longer cladodes (flattened stem portions), 35–75 cm (14–30 in) long, and longer tepals, 7–10 cm (3–4 in) long. D. a. var. conzattianum has shorter cladodes, 10–50 cm (4–20 in) long, shorter hypanthia, 2.8 cm (1.1 in) long, and shorter tepals, 4–6 cm (1.6–2.4 in) long.[2][4]
^ abBravo-Hollis, Helia; Sánchez-Mejorada, Hernando (1978). Las Cactáceas de México (in Spanish). Vol. 1. México: Universidad Nacional Autónoma de México. pp. 509–512.