| Hatiora | |
|---|---|
 | |
| Hatiora salicornoides | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Cactaceae |
| Subfamily: | Cactoideae |
| Tribe: | Rhipsalideae |
| Genus: | Hatiora Britton &Rose[1] |
| Type species | |
| Hatiora salicornoides (Haw.) Britton & Rose | |
| Species | |
See text | |
| Synonyms | |
| |
Hatiora is a smallgenus ofepiphytic cacti which belongs to the tribeRhipsalideae within the subfamilyCactoideae of theCactaceae. Recenttaxonomic studies have led to the three species formerly placed insubgenusRhipsalidopsis being removed from the genus, including the well known and widely cultivated ornamental plants known as Easter cactus or Whitsun cactus (cultivars or hybrids of the formerHatiora gaertneri).
AllHatiora species are found asepiphytes growing on trees or (rarely)lithophytes growing on rocks. They are found in thetropical rainforests of theMata Atlântica in easternBrazil. The plants are weaklysucculent, growing more or less upright and becoming woody at the base when older. Spines are usually missing. The insect-pollinatedflowers are borne terminally. They are small, with a diameter of about 2 cm (0.8 in),actinomorphic (radially symmetrical), bell-shaped and always coloured (yellow, yellow-orange or pink). Thefruit is aberry. By contrast with species of the genusSchlumbergera, most of which have flattened stems,Hatiora species have stems with a circular cross-section.[2][3]
Cacti belonging to the tribe Rhipsalideae are quite distinct in appearance and habit from other cacti, as they grow on trees or rocks asepiphytes orlithophytes. However, for a long time there has been confusion as to how the rhipsalid species should be divided into genera. In 1819,Haworth described the first discovered species of the modern genusHatiora under the nameRhipsalis salicornoides. In 1834,A.P. de Candolle recognized the distinctness of this species and transferred it to a new genusHariota, named afterThomas Hariot, a 16th-century botanist. Later a second species,H. gaertneri, was initially named asEpiphyllum russellianum var.gaertneri (Epiphyllum russellianum is nowSchlumbergera russelliana) and then in 1889 asEpiphyllum gaertneri. A third species,H. rosea, was described in 1912 asRhipsalis rosea.[2]
By 1923, many nomenclatural uncertainties and confusion had arisen over the nameHariota.Nathaniel Britton andJoseph Rose created a new nameHatiora as a taxonomicanagram ofHariota. Of the species known at the time, they placedHariota salicornioides inHatiora along withH. cylindrica; they had already placedH. gaertneri inSchlumbergera in 1913 and left it there; and they erected a new genus,Rhipsalidopsis, forH rosea. Two further species which have been assigned toHatiora were placed in various genera, including the originalHariota andRhipsalis.[2] According to Anderson,[2] the confusion among the Rhipsalideae was not clarified until work byWilhelm Barthlott andNigel Taylor in 1995, which placed six species inHatiora, divided between two subgenera.[4]
Phylogenetic studies usingDNA have led to a modification of the Barthlott and Taylor classification and the three species ofHatiora they placed in subgenusRhipsalidopsis have been transferred out of the genus. There is agreement thatHatiora epiphylloides should be placed inSchlumbergera (asSchlumbergera lutea). There is disagreement over the other two species. Some sources also include them in a broadly definedSchlumbergera,[1][5] others place them as the only two species in the genusRhipsalidopsis.[6][3]Hatiora and the most broadlycircumscribedSchlumbergera both branch from the tip and have short segments (less than 7 cm long).Hatiora has stems that are round in cross-section and radially symmetrical (actinomorphic) flowers, whereasSchlumbergera has flattened or otherwise angular stems and its flowers may be radially symmetrical or radially unsymmetrical (zygomorphic).[5]
In the taxonomic treatments of the genus by Barthlott & Taylor (1995)[4] and Hunt (2006),[7]Hatiora was divided into two subgenera with six accepted species, plus a hybrid created in cultivation. SubgenusRhipsalidopsis has subsequently been removed fromHatiora.[1][5][6][3]
| Image | Scientific name | Distribution |
|---|---|---|
| Hatiora cylindricaBritton & Rose | Brazil (Bahia, Minas Gerais and Rio de Janeiro) | |
| Hatiora herminiae(Porto & A.Cast.) Backeb. ex Barthlott | Brazil (Minas Gerais and São Paulo) | |
 | Hatiora salicornoides(Haworth) Britton & Rose ex L.H.Bailey | Brazil (Bahia, Espírito Santo, Minas Gerais, Rio de Janeiro state, São Paulo state and Paraná) |
