The Buxales are a small order of

eudicot The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicot ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s, recognized by the

APG IV system The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was publishe ...

of 2016. The order includes the family

Buxaceae The Buxaceae are a small family of six genera and about 123 known species of flowering plants. They are shrubs and small trees, with a cosmopolitan distribution. A seventh genus, sometimes accepted in the past (''Notobuxus''), has been shown by ...

; the families

Didymelaceae ''Didymeles'' is a genus of flowering plants. It is variously treated as the only genus of the family Didymelaceae — or in the family Buxaceae, as in the APG IV system. The genus ''Didymeles'' is restricted to Madagascar and the Comoros. In M ...

and

Haptanthaceae ''Haptanthus'' is a monotypic genus containing the sole species ''Haptanthus hazlettii'', a shrub or small tree known only from the locality of Matarras in the Arizona Municipality in Honduras. Its flowers are unique among the flowering plants ...

may also be recognized or may be included in the Buxaceae. Many members of the order are evergreen shrubs or trees, although some are herbaceous perennials. They have separate "male" (staminate) and "female" (carpellate) flowers, mostly on the same plant (i.e. they are mostly

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

). Some species are of economic importance either for the wood they produce or as

ornamental plant Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...

Description

The Buxales have relatively few obvious shared features distinguishing them from related groups of plants (i.e. few obvious

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

). One is the presence of a particular type of

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...

or pseudoalkaloid, pregnane steroids. They have unisexual flowers (i.e. separate staminate or "male" flowers and carpellate or "female" flowers), most being

. The flowers are small, less than 7 mm across. The

tepal A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...

s have a single

vascular bundle A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in the stem, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will inclu ...

(trace). Other characters common to the order include leaves with entire (untoothed) margins, flowers arranged in

raceme A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...

s, small

style Style is a manner of doing or presenting things and may refer to: * Architectural style, the features that make a building or structure historically identifiable * Design, the process of creating something * Fashion, a prevailing mode of clothing ...

s capable of receiving pollen along their entire length rather than having a separate stigma, one to two

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fe ...

s per

carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...

, and seeds with testae (coats) made up of several cell layers. ''

Didymeles ''Didymeles'' is a genus of flowering plants. It is variously treated as the only genus of the family Didymelaceae — or in the family Buxaceae, as in the APG IV system. The genus ''Didymeles'' is restricted to Madagascar and the Comoros. In M ...

'', the sole genus in the family

, consists of two species of evergreen tree occurring only in

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

. It is dioecious, i.e. with staminate and carpellate flowers on separate plants.

(including

) is more diverse, with five or six genera totalling about 115 species, and is found in most temperate and tropical areas of the world. Most species are evergreen shrubs or small trees, but some (such as those of ''

Pachysandra ''Pachysandra'' is a genus of five species of evergreen perennials or subshrubs, belonging to the boxwood family Buxaceae. The species are native to eastern Asia and southeast North America, some reaching a height of , with only weakly woody s ...

'') are herbaceous perennials.

Taxonomy

In the

APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a fur ...

of 2009, the order includes two families,

and

. Unlike previous classifications (including the

APG II system The APG II system (Angiosperm Phylogeny Group II system) of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Gro ...

of 2003), APG III does not recognize the family

, but includes the genus ''

'' in Buxaceae. Subsequent research published in 2011 suggests that the Haptanthaceae are embedded in the Buxaceae, possibly as the sister to ''

Buxus ''Buxus'' is a genus of about seventy species in the family Buxaceae. Common names include box or boxwood. The boxes are native to western and southern Europe, southwest, southern and eastern Asia, Africa, Madagascar, northernmost South ...

'', and the

Angiosperm Phylogeny Website The Angiosperm Phylogeny Website (or APweb) is a website dedicated to research on angiosperm phylogeny and taxonomy. The site is hosted by the Missouri Botanical Garden website and maintained by researchers, Peter F. Stevens and Hilary M. Davis ...

no longer recognizes Haptanthaceae. In the 2016

, Haptanthaceae is incorporated into Buxaceae, which leaves Buxaceae the only family under ''Buxales''.

Phylogeny

The Buxales are placed within the

eudicots The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dico ...

but outside the

core eudicots The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicots ...

, in a paraphyletic group of basal eudicots. The

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

of the order and its general position relative to other eudicots has been confirmed by many studies. One possible phylogenetic tree is shown below, where the precise ordering of the basal eudicots is still uncertain. One difference between the basal eudicots and the core eudicots is that the latter appear to have undergone a complete duplication of the nuclear genome which is absent in the former. Molecular phylogenetic studies have produced slightly different internal arrangements of the families and genera within the order; hence the variation in the number of families into which it is divided.

Genera

Didymelaceae or Buxaceae * ''

'' Thouars Buxaceae * ''

'' L. (including ''Notobuxus'' Oliver) * ''

'' Michx. * ''

Sarcococca ''Sarcococca'' (sweet box or Christmas box) is a genus of 11 species of flowering plants in the box family (biology), family Buxaceae, native plant, native to eastern and southeastern Asia and the Himalayas. They are slow-growing, monoecious, eve ...

'' Lindl. * '' Styloceras'' Kunth ex A.Juss. Buxaceae or Haptanthaceae * ''

Haptanthus ''Haptanthus'' is a monotypic genus containing the sole species ''Haptanthus hazlettii'', a shrub or small tree known only from the locality of Matarras in the Arizona Municipality in Honduras. Its flowers are unique among the flowering plants ...

'' Goldberg & C.Nelson

Former treatment

In the

Cronquist system The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of Flowering Plants'' (1968; 2nd edition, 1988) a ...

of 1981, the Buxaceae were associated with the

Euphorbiaceae Euphorbiaceae, the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of a genus in the family. Most spurges, such as ''Euphorbia paralias'', are herbs, but some, e ...

s.l., and the Didymelaceae were given their own order. In the

of 2003, the

were a family unplaced as to order in the

, optionally including the genus ''

'', which could alternatively be placed in its own family.

Uses

Some species of the Buxaceae are of economic importance. ''

Buxus sempervirens ''Buxus sempervirens'', the common box, European box, or boxwood, is a species of flowering plant in the genus ''Buxus'', native to western and southern Europe, northwest Africa, and southwest Asia, from southern England south to northern Morocco ...

'' (common box) and ''

Buxus macowanii ''Buxus macowanii'', aka Cape box, is an evergreen species of boxwood endemic to South Africa, where it occurs in two disjunct populations - in coastal forest and shady ravines from the Eastern Cape to southern Natal, and in the Waterberg of the ...

'' (Cape box) produce hard wood valued for carving and engraving. Species are also used as ornamental garden plants and for

bonsai Bonsai ( ja, 盆栽, , tray planting, ) is the Japanese art of growing and training miniature trees in pots, developed from the traditional Chinese art form of ''penjing''. Unlike ''penjing'', which utilizes traditional techniques to produce ...

. Common box is used for hedging and border edging. Species of ''

'' are used as ground cover. Species of ''

'' produce small but strongly scented flowers in the winter.

References

{{Taxonbar, from=Q21020 Angiosperm orders Eudicots Monotypic plant orders