Britton & Rose
Hariota DC., Rhipsalidopsis Britton & Rose
Hatiora is a small genus of epiphytic cacti which belongs to the tribe Rhipsalideae within the subfamily Cactoideae of the Cactaceae. Some Hatiora species are well known and widely cultivated ornamentals, known as Easter cactus or Whitsun cactus. Recent taxonomic studies have led to the three species of subgenus Rhipsalidopsis being transferred into the closely related genus Schlumbergera, though this change has not been widely adopted.
All Hatiora species are found as epiphytes growing on trees or (rarely) lithophytes growing on rocks. They occur only in the tropical rainforests of the Mata Atlântica in south-eastern Brazil. The plants are weakly succulent, growing upright or pendent; spines are usually missing. The flowers are borne terminally; they are actinomorphic (radially symmetrical) and are always coloured. The fruit is a berry.
Hatiora species have been divided into two groups or subgenera which are well differentiated by their morphology. Members of subgenus Hatiora have cylindrical stems. They grow more or less upright and become woody at the base of the stems when plants become older. The flowers are small, with a diameter of about 1 cm (0.4 in), and yellow, orange or pink. Members of subgenus Rhipsalidopsis have flattened, weakly succulent, segmented stems. The flowers of this subgenus are large and usually red or pink, but yellow in Hatiora epiphylloides.
Name and synonyms
Cacti belonging to the tribe Rhipsalideae are quite distinct in appearance and habit from other cacti, as they grow on trees or rocks as epiphytes or lithophytes. However, for a long time there was confusion as to how the rhipsalid species should be divided into genera. In 1819, Haworth described the first discovered species of the modern genus Hatiora under the name Rhipsalis salicornioides. In 1834, A.P. de Candolle recognized the distinctness of this species and transferred it to a new genus Hariota, named after Thomas Hariot, a 16th-century botanist. Later a second species, H. gaertneri, was initially named as Epiphyllum russellianum var. gaertneri (Epiphyllum russellianum is now Schlumbergera russelliana) and then in 1889 as Epiphyllum gaertneri. A third species, H. rosea, was described in 1912 as Rhipsalis rosea.
By 1923, many nomenclatural uncertainties and confusion had arisen over the name Hariota. Nathaniel Britton and Joseph Rose created a new name Hatiora as an anagram of Hariota. Of the species known at the time, they placed Hariota salicornioides in Hatiora along with H. cylindrica; they had already placed H. gaertneri in Schlumbergera in 1913 and left it there; and they erected a new genus, Rhipsalidopsis, for H. rosea. When two further species of the modern genus were discovered, they were placed in various genera, including the original Hariota and Rhipsalis. According to Anderson, the confusion among the Rhipsalideae was not clarified until work by Wilhelm Barthlott and Nigel Taylor in 1995. However, recent phylogenetic studies using DNA have led to a modification of this classification and three species of Hatiora have been transferred into Schlumbergera.
The formal synonyms of the genus Hatiora are:
- Hariota DC., in part, non Adans. (Hariota Adans. is a synonym of Rhipsalis)
- Rhipsalidopsis Britton & Rose
- Epiphyllopsis (A.Berger) Backeb. & F.M.Knuth
- Pseudozygocactus Backeb.
Subgeneric classification and species
Based on the latest taxonomic treatments of the genus by Barthlott & Taylor and Hunt, Hatiora is divided into two subgenera with six accepted species, plus a hybrid created in cultivation. Subgenus Rhipsalidopsis has recently been transferred into Schlumbergera, though this change has yet to be adopted by many Cactaceae authorities.
- Subgenus Hatiora
- Subgenus Rhipsalidopsis
- Hatiora epiphylloides (Porto & Werderm.) Buxb. [Now Schlumbergera lutea Calvente & Zappi]
- Hatiora gaertneri (Regel) Barthlott [Now Schlumbergera gaertneri (Regel) Britton & Rose]
- Hatiora rosea (Lagerh.) Barthlott [Now Schlumbergera rosea (Lagerh.) Calvente & Zappi]
- Hatiora × graeseri (Werderm.) Barthlott ex D.R.Hunt, an artificial hybrid of H. gaertneri and H. rosea [Now Schlumbergera x graeseri (Barthlott ex D.R.Hunt) D.R.Hunt]
- Calvente, Alice; Zappi, Daniela C; Forest, Félix; Lohmann, Lúcia G (2011-03-01). "Molecular phylogeny of tribe Rhipsalideae (Cactaceae) and taxonomic implications for Schlumbergera and Hatiora". Molecular Phylogenetics and Evolution. 58 (3): 456–468. doi:10.1016/j.ympev.2011.01.001. ISSN 1055-7903. PMID 21236350.
- Anderson 2001, pp. 375–377
- Barthlott & Taylor 1995
- Hunt 2006
- Anderson, Edward F. (2001), The Cactus Family, Pentland, Oregon: Timber Press, ISBN 978-0-88192-498-5
- Barthlott, W. (1987), "New names in Rhipsalidinae", Bradleya, 5 (5): 97–100, doi:10.25223/brad.n5.1987.a7
- Barthlott, W. & Taylor, N.P. (1995), "Notes towards a monograph of Rhipsalidaeae (Cactaceae)", Bradleya, 13 (13): 43–79, doi:10.25223/brad.n13.1995.a7
- Britton, N.L. & Rose, J.N. (1919–1923), The Cactaceae : descriptions and illustrations of plants of the cactus family, Washington: Carnegie Institute, OCLC 491535615
- Friedman, K.A. (1980), "Hatiora Britton & Rose", Cactus and Succulent Journal, 52: 127–129
- Hunt, David R., ed. (2006), The New Cactus Lexicon (2 volumes), Milborne Port: dh books, ISBN 978-0-9538134-4-5
- Taylor, N.P. & Zappi, D.C. (2004), Cacti of Eastern Brazil, London: Kew Publishing, ISBN 978-1-84246-056-6
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