Buxaceae Dumort.

Flora Zambesiaca. Vol. 9, Part 3. Polygonaceae-Myriaceae. Pope GV, Polhill RM, Martins ES. 2006.

Morphology General Habit

Trees or shrubs, rarely herbs Trees or shrubs, rarely herbs

Morphology Leaves

Leaves simple, opposite, rarely alternate, usually coriaceous, evergreen, with entire margin, rarely toothed (only in the Asian genus Pachysandra); stipules absent Leaves simple, opposite, rarely alternate, usually coriaceous, evergreen, with entire margin, rarely toothed (only in the Asian genus Pachysandra); stipules absent

Morphology Reproductive morphology Flowers

Female flowers usually much larger than male ones, with 4–6 perianth segments; staminodes absent; ovary superior, 3-locular, with 3 entirely free basally connate styles which are often grooved along the upper surface; ovules 1–2 per locule, pendulous, anatropous Male flowers with 4 perianth segments and 4–6(10) stamens, rarely (only in the South American genus Styloceras and the North American genus Simmondsia) stamens numerous, opposite the perianth segments, or with more stamens at each perianth segment, when stamens 6 then usually 2 opposite the inner pair of perianth segments; filaments present or absent; rudimentary ovary present or absent Flowers small, unisexual (very rarely some in an individual bisexual), usually in dense bracteate spikes, fascicles or cymes, monoecious or rarely dioecious; perianth segments sepal-like, membranous or apparently absent Flowers small, unisexual (very rarely some in an individual bisexual), usually in dense bracteate spikes, fascicles or cymes, monoecious or rarely dioecious; perianth segments sepal-like, membranous or apparently absent Female flowers usually much larger than male ones, with 4–6 perianth segments; staminodes absent; ovary superior, 3-locular, with 3 entirely free basally connate styles which are often grooved along the upper surface; ovules 1–2 per locule, pendulous, anatropous Male flowers with 4 perianth segments and 4–6(10) stamens, rarely (only in the South American genus >i>Styloceras and the North American genus >i>Simmondsia) stamens numerous, opposite the perianth segments, or with more stamens at each perianth segment, when stamens 6 then usually 2 opposite the inner pair of perianth segments; filaments present or absent; rudimentary ovary present or absent

Note

The systematic position of the family is still unclear. Although the family resembles the Euphorbiaceae in a number of easily observed morphological characters (especially the unisexual flowers with 3-merous ovary and 3 free or almost free styles and stigmas), it is clearly separated from the Euphorbiaceae in characters of the ovule; a number of characters from seed anatomy and phytochemistry suggest relationship with various small families normally placed in the Hamamelidales sensu lat. (see review by Jarvis in Crane & Blackmore (eds.), Evolution, Systematics and Fossil History of the Hamamelideae, 1. Systematics Association, Special Vol. No. 40A: 273–278 (1989)).

Distribution

A family of 2–7 genera (depending upon the generic circumscription and the inclusion or exclusion of the segregate families Simmondsiaceae (only the genus Simmondsia), Pachysandraceae (only genus Pachysandra), and the Styloseranthaceae (only genus Styloce

sex Male

Male flowers with 4 perianth segments and 4–6(10) stamens, rarely (only in the South American genus >i>Styloceras and the North American genus >i>Simmondsia) stamens numerous, opposite the perianth segments, or with more stamens at each perianth segment, when stamens 6 then usually 2 opposite the inner pair of perianth segments; filaments present or absent; rudimentary ovary present or absent

sex Female

Female flowers usually much larger than male ones, with 4–6 perianth segments; staminodes absent; ovary superior, 3-locular, with 3 entirely free basally connate styles which are often grooved along the upper surface; ovules 1–2 per locule, pendulous, anatropous

Morphology Reproductive morphology Fruits

Fruit a capsule or drupe, often with a detaching endocarp at maturity Fruit a capsule or drupe, often with a detaching endocarp at maturity

Morphology Reproductive morphology Seeds

Seeds black and shiny; endosperm fleshy Seeds black and shiny; endosperm fleshy.

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit

Trees or shrubs, rarely herbs, monoecious or rarely dioecious

Morphology Leaves

Leaves simple, opposite or rarely alternate, usually leathery, evergreen, with entire margin, rarely toothed (only in Pachysandra); stipules absent

Morphology Reproductive morphology Flowers

Flowers small, unisexual, usually in dense spikes, clusters or cymes; perianth segments sepal-like, membranous or apparently absent Male flowers with 4 tepals and 4–6(–10) stamens, or rarely stamens numerous, when stamens 6 then usually 2 opposite the inner pair of tepals, filaments present or absent; rudimentary ovary present or absent Female flowers usually much larger than male ones, with 4–6 tepals, staminodes absent; ovary superior, 3-celled, with 3 entirely free or basally connate styles; ovules 1–2 per cell, pendulous, anatropous

Morphology Reproductive morphology Fruits

Fruit a loculicidally dehiscent capsule or a drupe, often with a detaching endocarp at maturity

Morphology Reproductive morphology Seeds

Seeds black and shining; endosperm fleshy.

Distribution

Family of six genera and about 130 species, widely distributed in all warmer parts of the world, except South America. In Africa only two genera.

Note

The systematic position of Buxaceae is still unclear. Although the family resembles Euphorbiaceae in various easily observed morphological characters (unisexual flowers with 3-merous ovary and 3 free or almost free styles and stigmas), it is very distinct from that family in other characters. A number of characters suggest a relationship with Hamamelidales; see Jarvis in Systematics Ass., Special Vol. No. 40A: 273–278 (1989).

Köhler, E. (2009). Neotropical Buxaceae.

Morphology

Description

Evergreen shrubs, trees (to 15 m tall). Stipules absent. Leaves alternate (Styloceras Kunth ex A.Juss.and Sarcococca Lindl.) or decussate (Buxus L.), simple , petiolate , rarely sessile , blades with bases decurrent as internodial folds on the branchlets (Buxus), margins entire , venation pinnate , less often ± tripli-veined. Inflorescences axillary , less frequent terminal , racemes, clusters, or spikes, sometimes of solitary pistillate flowers (Styloceras), the racemes loose to densely glomerate, with single apical female flower  (Buxus), the clusters or spikes often erect with apical staminate flowers (Sarcococca), these sometimes pendent (Styloceras), the flowers subtended by bracts and bracteoles (Sarcococca). Flowers actinomorphic , unisexual, plants monoecious or dioecious (some Styloceras), small. Staminateflowers: tepals 2+2, inconspicuous, bract -like or sometimes petal -like or lacking (Styloceras); petals absent; androecium usually with 4 stamens, opposite the tepals, or stamens numerous (Styloceras), inserted on angular- ovate bracts, the stamens usually inserted around a pistillode, nectariferous (lacking in Styloceras), anthers dorsifixed to basifixed, tetrasporangiate, longitudinally dehiscent , with protruding connective tip. Pistillateflowers: tepals 4-6, bract -like; petals absent; gynoecium syncarpous, the ovary superior , the carpels (2-)3(-4) with free , sometimes large divergent styles (Styloceras), rarely connate at the base, persistent on fruit (Buxus), the stigma decurrent along the ventral fold, nectariferous protuberances occuring between styles (Buxus, possibly of androecial origin); the locules (2-)3(-4), sometimes with false septa, divided into uni-ovulate locelli (Styloceras and Pachysandra Michx.); placentation axile ; ovules usually 2 per locule , pendent, anatropous, bitegmic. Fruits capsules (Buxus), drupe-like (Sarcococca and Styloceras); capsules dehiscing loculicidally into 3 spreading, 2-horned valves, the exocarp chartaceous , the detaching endocarp cartilaginous , partly enclosing and ejecting the seeds; drupaceous fruits with a pulpy mesocarp and a thin crustaceous or cartilaginous endocarp , divided in 4-6 pyrenes (Styloceras). Seeds usually (2-)4-6 black or blue, shining, caruncle present (Buxus); endosperm copious, fleshy , oily, the cotyledons thin, flat.

General Description

Notes on delimitation

• The family comprises two subfamilies, the Buxoideae and Styloceratoideae, supported by recent molecular data as two major clades.
• Styloceras is sometimes regarded as a separate family, and is recognized as a sister group of Sarcococca and Pachysandra.
• The rank of Notobuxus Oliv. is still in discussion. It was recently treated as a subgenus of Buxus, but deviates in the number of stamens, the chromosome number, and features of the exine.
• The family has frequently been associated with Euphorbiaceae, but Celastrales and Hamamelidales have also been considered.
• Recent morphological and molecular data place Buxaceae as sister to Didymelaceae (Buxales) together with Ranunculales, Sabiaceae, Proteales and Trochodendraceae in a grade at the base of the eudicots.

General notes

• The family has a disjunct intercontinental distribution with centers of diversity in tropical and temperate East Asia and in the Caribbean.
• In the Western Hemisphere the family is distributed from south-eastern United States (one species of Pachysandra) to Andean South America (five species of Styloceras) and the Caribbean coast of northern South America.
• One species of Sarcococca is recorded from Guatemala and southern Mexico.
• The largest and most widespread genus, Buxus, has a marked center of diversity in Cuba.
• The genus Buxus is economically important for its horticultural value. More than 150 registered cultivars, mainly of B. sempervirens L. and B. microphylla Sieb. & Zucc., are used for edging, for pruning and for topiary work. The closely grained wood is employed for turning, engraving and manufacturing musical instruments.
• Styloceras provides first class timber for joinery.

Status

• Styloceras is endemic to South America.
• Buxus has native representatives in the Neotropics.
• Sarcococca is a mainly East Asian genus with 1 species in Guatemala and Mexico, still of doubtful generic affiliation.

Number of genera

5 genera worldwide (3 in Neotropics)

• Buxus
• Notobuxus
• Pachysandra
• Sarcococca
• Styloceras

Distribution

Distribution in the Neotropics

• Buxus - Mexico, Mesoamerica, Caribbean, Caribbean coast of northern South America.
• Sarcococca - southern Mexico, Guatemala (1 species, generic position doubtful, Sealy 1986).
• Styloceras - Andean South America, Bolivia, Ecuador, Peru, Venezuela.

Diagnostic

Other important characters

• Stamens 4, opposite the tepals.

OR

• Stamens numerous, then tepals wanting.

Distinguishing characters (always present)

• Small unisexual flowers.
• Actinomorphic.
• Mostly with tepals.
• Petals absent.
• Carpels (2)3(4).
• Syncarpous.
• 2 ovules per locule.
• Divergent styles.
• Stipules absent, leaves with pinnatevenation.

Notable genera and distinguishing features

Buxus:

• Tetragonal branchlets.
• Leaves decussate.
• Flowers in lax to glomerate racemes with a terminal female flower.
• Staminate 4-merous tepals and stamens.
• Tepals decussate.
• Stamens opposite tepals, inserted around a pistillode.
• Fruit a 3-horned capsule.
• Dehiscing loculicidally into 3 spreading 2-horned valves.

Sarcococca: 

• Shrubs.
• Small trees.
• Leaves alternate.
• Inflorescences with female flowers above (in Neotropics).
• Staminate 4-merous tepals and stamen.
• Tepals and stamen whitish.
• Fruit white, indehiscent, subdrupaceous, with dry mesocarp.

Styloceras:

• Trees or shrubs.
• Dioecious, rarely monoecious.
• Staminate flowers in short pendent spikes.
• Tepals absent.
• Several stamens inserted on an angular-ovatebract.
• Pistillode absent.
• Fruitglobose, yellow, dupraceous, ± fleshy, indehiscent or tardily dehiscent.

Useful tips for generic identification

Key to genera of Neotropical Buxaceae

1. Tepals absent, male flowers in pendent spikes, stamens numerous, inserted on bracts, ovary 2(3)carpellate ...Styloceras
1. Tepals present, stamens usually four ... 2

2. Leaves decussate, female flowers terminal in racemes or clusters, fruit a 3-valved capsule...Buxus
2. Leaves alternate, female flowers, normally at base of racemes, in the Neotropics as uppermost, fruit subdrupaceous ...Sarcococca

Literature

Important literature

Balthazar, M. von & Endress, P.K. 2002. Reproductive structures and systematics of Buxaceae. Bot. J. Linn. Soc. 140:193-228.

Balthazar, M. von & Endress, P.K. 2002. Development of inflorescences and flowers in Buxaceae and the problem of perianth interpretation. Intl.J.Pl.Sci. 163:847-876.

Balthazar, M. von, Endress, P.K. & Qiu, Y.-L. 2000. Phylogenetic relationships in Buxaceae based on nuclear internal transcribed spacers and plastid ndhF sequences. Intl.J.Pl.Sci. 161:785-792.

Batdorf, L.R. 2005. Boxwood Handbook. Boyce: American Boxwood Society.

Gentry, A.H. & Foster,R. 1981. A new Peruvian Styloceras (Buxaceae): discovery of a phytogeographical missing link. Ann. Missouri Bot. Gard. 68:122-124.

Gentry, A.H. & Aymard, G. 1993. A new species of Styloceras (Buxaceae) from Peru. Novon 3:142-144.

Köhler, E. 1981. Pollen Morphology of the West-Indian-Central American species of the Genus Buxus L. (Buxaceae) with reference to taxonomy. Pollen et Spores 23:37-91.

Köhler, E. 1993. Blattnervatur-Muster der Buxaceae Dumortier und Simmondsiaceae van Tieghem. Feddes Repertorium 104:145-167.

Köhler, E. & Brückner, P. 1990. Considerations on the evolution and chorogenesis of the genus Buxus (Buxaceae). Mem. New York Bot. Gard. 55:153-168.

Köhler, E., Fernández, R. & Zamudio, S. 1993. Buxus moctezumae Köhler, Fernández & Zamudio (Buxaceae) una especie nueva de Estado de Querétero, México. Feddes Repertorium 104:295-305.

Köhler, E. 2004. Buxaceae. In: N.Smith, S.A.Mori, A.Henderson. D.W.Stevenson & S.V.Head (eds.), Flowering Plants of the Neotropics: 70-72. Princeton, Princeton University Press.

Köhler, E. 2006. Three new Buxus species (Buxaceae) from eastern Cuba. Willdenowia 36: 479-489.

Mathou, Th. 1940. Recherches sur le famille des Buxacées. Toulouse:Douladoure.

Sealy, J.R. 1986. A revision of the genus Sarcococca (Buxaceae). Bot. J. Linn. Soc.92: 117-159.

Buxaceae, Hutchinson and Dalziel. Flora of West Tropical Africa 1:2. 1958

Morphology General Habit

Trees or shrubs, rarely herbs

Morphology Leaves

Leaves evergreen, alternate or opposite, simple; stipules absent

Morphology Reproductive morphology Flowers

Flowers unisexual, monoecious or dioecious, spicate or fasciculate Female flowers often larger than the males and fewer or solitary

Morphology Reproductive morphology Flowers Corolla

Petals absent

Morphology Reproductive morphology Flowers Androecium

Stamens 4 or 6, rarely more; anthers large, sessile or stalked, cells 2-valved or opening lengthwise

Morphology Reproductive morphology Flowers Sterile Parts

Rudimentary ovary sometimes present

sex Female

Female flowers often larger than the males and fewer or solitary

Morphology Reproductive morphology Flowers Calyx

Sepals as in the males Sepals imbricate or absent, usually 4

Morphology Reproductive morphology Flowers Gynoecium

Ovary superior, 3-celled; styles undivided Ovules 1–2, pendulous, anatropous

Morphology Reproductive morphology Fruits

Fruit a capsule or drupe

Morphology Reproductive morphology Seeds

Seeds black, shining, with fleshy endosperm and straight embryo

Every, J.L.R. (2009). Neotropical Haptanthaceae.

Morphology

Description

Evergreen broad-leaved tree (or shrub ?). Leaves opposite, simple , entire , glabrous ; estipulate. Inflorescence axillary , cymose, pedunculate. Flowers unisexual, monoecious , bracteate; staminate flowers with 2 leaf-like stamens and tepals absent, or 2 tepals with adnate stamens, anthers dehiscing via longitudinal slits, dorsifixed; pistillate flowers with 4 tepals, ovary superior , syncarpous, carpels 3, placentation parietal , stigmas 3. Fruit unknown.

General Description

Notes on delimitation

• Described in 1989 as Haptanthushazlettii Goldberg & C. Nelson and placed in its own family.
• Placed in the Buxales by the APG on morphological grounds (Stevens 2008).

Number of genera

• 1: Haptanthushazlettii.

Distribution

Distribution in the Neotropics

• Found on a single occasion in the rainforest of central Honduras in 1980, rediscovered in April 2010.

Diagnostic

Distinguishing characters (always present)

• Evergreen.
• Monoecious.
• Staminate flowers with two elliptic flattened structures.

Key differences from similar families

• The single collection has been compared to many families but due to the lack of information it has proved very difficult to identify distinct differences. The morphology of the flowers appears to be distinct from the listed families: Achariaceae, Buxaceae, Capparaceae, Chloranthaceae, Euphorbiaceae, Hamamelidaceae, Lacistemataceae, Salicaceae, Saururaceae.  

Literature

Important literature

Goldberg, A. & Nelson, C. 1989. Haptanthus, a New Dicotyledonous Genus from Honduras. Systematic Botany: 14(1): 16-19.

Heywood, V.H. 2007. Haptanthaceae. In: V.H. Heywood, R.K. Brummitt, A. Culham and O. Seberg (eds.). Flowering plant families of the world. P.164. Royal Botanic Gardens, Kew.

Maas, P.J.M. & Westra, L.Y.Th. 2005. Neotropical Plant Families. 358 pp. 3rd ed. A.R.G. Gantner Verlag K.G., Ruggell.

Stevens, P.F. 2008. Angiosperm Phylogeny Website. Version 9 onwards. http://www.mobot.org/MOBOT/research/APweb/

Stevens, P.F. & Doust, A.N. 2005. A Reinterpretation of the Staminate Flowers of Haptanthus. Systematic Botany 30(4): 779-785.