Haworthiopsis
Haworthiopsis is a genus of succulent plants in the subfamily Asphodeloideae. The genus was previously included in "Haworthia". Species in the genus are typically short perennial plants, with leaves often arranged in a rosette and frequently having raised white markings. The two-lipped flowers are borne on a tall stalk and are small – less than long – and pale in colour. Many species are cultivated as house plants or by succulent enthusiasts. Description. "Haworthiopsis" species are short perennial plants, with or without an obvious stem. The leaves either form a rosette or are arranged in a spiral on a more  extended stem. Individual leaves are smooth or have white markings, which may take the form of small protuberances (tubercules) or be more pointed, almost spine-like. The white markings may be on the lower surface of the leaf only, or on both surfaces, and may also extend to the leaf margins. The upper leaf surfaces are "windowed" in some species, and the margins may have toughened teeth. The flowers are borne in a raceme on a long, stiff stalk (peduncle) which also bears a few bracts without flowers in their junctions with the stalk. Each flower is less than long , with white to green, pink or brown tepals, forming a two-lipped (bilabiate) structure with a hexagonal or rounded hexagonal base. Both the outer and inner tepals are joined together at their bases. The stamens and the style are enclosed within the tepals. The fruit is a narrowly ovoid capsule with black or dark brown seeds. Two-lipped flowers were considered a distinguishing characteristic of the genus "Haworthia", before "Haworthiopsis" and "Tulista" were split off. More detailed features of the flowers now identify the three genera. In "Haworthiopsis", the flowers and their styles are usually straight rather than curved; the  outer and inner whorls of three tepals are joined to one another at the base; and the flowers taper smoothly into the flower stem (pedicel) rather than being broader at the base with a sharp junction. Taxonomy. The genus "Haworthiopsis" was erected by Gordon Rowley in 2013, with the type species "Haworthiopsis coarctata". The ending "-opsis" derives from the Greek (opsis), meaning 'appearance', hence "Haworthiopsis" means "like "Haworthia"". The taxonomic history of the genus is complex. In 1753, Carl Linnaeus followed authors before him in using the genus "Aloe" for a wide range of plants now placed in the tribe  Aloeae by those using the broad circumscription of the family Asphodelaceae ("sensu" APG III onwards). Linnaeus's "Aloe" species included two now placed in "Haworthiopsis". The genus "Haworthia" was established by Henri Auguste Duval in 1809 for former "Aloe" species with smaller whitish two-lipped (bilabiate) flowers. Many additional taxa were later added, at both species and infraspecies ranks. This has been described as "causing a great deal of confusion". In 1971, M.B. Bayer divided "Haworthia" into three subgenera: "H." subg. "Haworthia", "H." subg. "Hexangulares" and "H." subg. "Robustipedunculatae". Phylogenetic studies, particularly from 2010 onwards, showed that "Haworthia" and other  genera related to "Aloe" were not monophyletic. Accordingly, in 2013, Rowley separated most of the species formerly placed in "Haworthia" subg. "Hexangulares" into a new genus, "Haworthiopsis". "Haworthiopsis" was revised in 2013 by Manning et al. so that the genus more closely correlated with the former subgenus, a revision described as "more coherent" by Gildenhuys and Klopper in 2016. Sections and Species. In 2016, Gildenhuys and Klopper proposed a division of the genus into seven sections, although noting that it could need re-evaluation when further phylogenetic studies had been carried out. Their section "Koelmaniorum" is least clearly placed in  the genus, and the status of sections "Limifoliae" and "Tessellatae" is also uncertain. , the World Checklist of Selected Plant Families accepted the following species: