1
MALPIGHIALES: AN INTRODUCTION
Petra Hoffmann
Malpighiales Mart. is a plant order containing 28 to 37 families (depending on the taxonomic concept
adopted), c. 725 genera, and 16,000 to 17,000 species. Ranked by approximate species number, the six
largest families are Euphorbiaceae J.F. Gmel. sensu stricto (6300 spp.), Phyllanthaceae Martynov
(2000 spp.), Clusiaceae Lindl. (1000 – 1500 spp.), Malpighiaceae Durande (1250 spp.), Salicaceae
Mirb. sensu lato (>1000 spp.) and Violaceae (800 – 900 spp.). See the table below for a full list of
Malpighiales families.
Malpighiales are mainly tropical, but some genera such as Euphorbia (spurge), Hypericum (St. John's
wort), Linum (flax), Salix (willow) and Viola (violet) are well-known in northern temperate regions.
The order contains one of the major starch-crops worldwide (cassava in Euphorbiaceae) and a number
of tropical fruit crops such as passion fruit (Passifloraceae) and mangosteen (Clusiaceae). The rubber
tree (Euphorbiacae) played an important role in the industrial revolution.
Cultivated ornamental plants include the climbing passion flowers (Passifloraceae), St. John's wort
(Hypericaceae or Clusiaceae-Hypericoideae), poinsettias (Euphorbiaceae), and violets and pansies
(Violaceae). Willows (Salicaceae) are used as a raw material for basket makers and hide tanners, in
environmental forestry (erosion control and land reclamation), and are being explored as an alternative
energy source. Linum usitatissimum L. (common flax) is an important fibre and oil plant.
The order Malpighiales is also notable for the high concentration of plants containing medicinally
active compounds, drugs and poisons. Outstanding examples are Erythroxylum coca Lam.
(Erythroxylaceae) yielding cocain, the castor oil plant Ricinus communis L. (Euphorbiaceae), Ryania
(Salicaceae sensu lato), Hydnocarpus (Achariaceae sensu lato, traditionally used in the treatment of
leprosy), and the St. John's wort, Hypericum perforatum L. (Hypericaceae or ClusiaceaeHypericoideae). Salicin extracted from willow bark is the origin of the pain and fever relief today
synthesised as aspirin (acetylsalicylic acid).
FAMILY
GENERA/ SPECIES
PREVIOUS TAXONOMIC
PLACEMENT(S)
DISTRIBUTION
Achariaceae
30/145
Violales
Pantropical
Balanopaceae
1/9
Balanopales, Fagales,
Buxales, etc.
New Caledonia,
Queensland, SW Pacific
Bonnetiaceae
3 – 4/c. 35
Theales, Guttiferales
Neotropical, 1 genus in
Malesia
Caryocaraceae
2/c. 25
Theales
Tropical America, esp.
Amazonia
Centroplacaceae
1/1
Euphorbiales
West-Central Africa
Chrysobalanaceae
17/c. 450
Rosales
Pantropical, esp. America
Clusiaceae
c. 30/1000 – 1500
Theales, Guttiferales
Worldwide
Ctenolophonaceae
1/3
Linales
W Africa, Malesia
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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FAMILY
GENERA/ SPECIES
PREVIOUS TAXONOMIC
PLACEMENT(S)
DISTRIBUTION
Dichapetalaceae
3/160 – 200
Euphorbiales, Celastrales
Pantropical, few in
Malesia
Elatinaceae
2/34
Theales, Guttiferales
Worldwide, mostly
tropical
Erythroxylaceae
4/c. 250
Linales, (Geraniales)
Pantropical, esp. America
Euphorbiaceae
220/c. 6300
Euphorbiales
Pantropical, extending
into temperate regions
Euphroniaceae
1/3
Polygalales
Northern tropical S
America (Guyana Shield)
Goupiaceae
1/1 – 3
Celastrales
NE South America
Humiriaceae
8/50
Linales, Geraniales
Tropical America, W
Africa
Hypericaceae
9/c. 470
Theales, Guttiferales
Worldwide
Irvingiaceae
3/c. 10
Sapindales, Rutales
Palaeotropical
Ixonanthaceae
4 – 5/ 20 – 30
Linales
Pantropical
Lacistemataceae
2/c. 15
Violales
Neotropical
Linaceae
10 – 15/150 – 300
Linales
Worldwide
Lophopyxidaceae
1/1 – 2
Celastrales
Malesia and W Pacific
Malesherbiaceae
1 – 2/27
Violales
Andean S America
Malpighiaceae
c. 65/c. 1250
Polygalales
Pantropical, esp. America
Medusagynaceae
1/1
Theales
Seychelles
Ochnaceae
28 – 35/370 – 600
Theales
Tropical, esp. Brazil
Pandaceae
3/c. 15
Euphorbiales
Palaeotropical
Passifloraceae
17 – 18/c. 550
Violales
Tropics to warm
temperate, esp. Africa and
America
Phyllanthaceae
59/c. 2000
Euphorbiales
Pantropical, esp. Malesia
Picrodendraceae
27/c. 80
Euphorbiales
Tropical, mainly southern
hemisphere
Podostemaceae
47 – 48/130 – 280
Podostemales
Tropical, esp. America
Putranjivaceae
2/c. 200
Euphorbiales
Palaeotropical
Quiinaceae
4/c. 50
Theales
Tropical America
Rafflesiaceae
3/20
Rafflesiales
South East Asia
Rhizophoraceae
15 – 16/120 – 150
Rhizophorales
Pantropical
Salicaceae
55/1010
Salicales
Pantropical, also northern
temperate to arctic
Trigoniaceae
3 – 5/c. 30
Polygalales
Tropical America,
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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FAMILY
GENERA/ SPECIES
PREVIOUS TAXONOMIC
PLACEMENT(S)
DISTRIBUTION
Madagascar, W Malesia
Turneraceae
10/110 – 120
Violales
Tropical to warm
America, and Africa to
Rodriguez I.
Violaceae
c. 20/800 – 900
Violales
Worldwide
Data compiled from various sources including Mabberley (1997), Stevens (2001), Watson & Dallwitz
(1992).
[all families in table should be linked to their respective place in the document]
Taxonomic history
The order was originally published by Martius (1835) as "Cohors Malpighinae", including the families
Vochysiaceae, Sapindaceae, Hippocastanaceae, Trigoniaceae, Moringaceae, Staphyleaceae,
Malpighiaceae, Erythroxylaceae, and Chailletiaceae (= Dichapetalaceae). It has not been recognised in
the plant classifications of the second half of the 20th century (e.g., Cronquist, Dahlgren, Takhtajan,
Thorne), when the family Malpighiaceae was most commonly classified in the order Polygalales.
In the 1990s, the ordinal classification of seed plants was revolutionised by DNA sequence data (e.g.
Chase & al. 1993). In many cases this method of phylogenetic analysis confirmed already established
orders to be natural (i.e. monophyletic) entities. Some of the groups of families defined by the
molecular work, however, were entirely new and surprising. Malpighiales was one of these, uniting
families from many diverse orders including Violales, Guttiferales, Euphorbiales, Linales, Theales,
Polygalales, Geraniales, Rosales, Malvales and several others.
The name Malpighiales was chosen (APG 1998) because it has not been used in the recent past and is
therefore relatively free from strong associations with traditional taxonomic circumscriptions.
Recently, molecular techniques using additional genes have extended the Malpighiales clade to
include, for example, Balanopaceae and Podostemaceae (Savolainen et al. 2000, Soltis et al. 2000) and
Rafflesiaceae (Barkman et al. 2004, Davis & Wurdack 2004, Nickrent et al. 2004).
As an order Malpighigiales is supported with more than 80% bootstrap support (Wurdack and Davis
unpublished manuscript). Most basal branches within the order, however, are only weakly supported
(less than 50% bootstrap support despite eight loci from all three genomes having been analysed by
Wurdack and Davis) and the relationships between the constituent clades are therefore uncertain. The
traditional circumscription of most families and some groups of closely related families (such as
Erythroxylaceae+Rhizophoraceae, Chrysobalanaceae+Euphroniaceae+Dichapetalaceae+Trigoniaceae
and Passifloraceae+Turneraceae+Malesherbiaceae) is confirmed in highly supported clades. The
exceptions are Euphorbiaceae sensu lato and Flacourtiaceae (now Achariaceae sensu lato and
Salicaceae sensu lato) which were found to split into several clades (discussed in more detail below).
Morphology and ecology
Malpighiales lack characters with high recognition value at ordinal level. A number of other
monophyletic groups defined by the phylogenetic Angiosperm Phylogeny Group classification (APG
2003) also present this problem and it is a major difficulty for users of the system. Gross morphology
in seed plants has often been found to be highly homoplasious, often in response to environmental
factors such as life-form and pollination syndromes. This is the case with Malpighiales, and any
description of the clade on the basis of character states universal to the group is likely to be rather
general.
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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Malpighiales can be large trees with brilliantly coloured flowers as in Clusiaceae, lianas with large and
complex flowers as in Passiflora, spiny succulents as in Euphorbia, or hygrophilous submerged or
emergent herbs and subshrubs in swamps or on lakesides (Elatinaceae) or even submerged thalloid
herbs without primary roots that are attached to rocks in flowing water (Podostemaceae). The
holoparasitic Rafflesiaceae live entirely within the host-tree (Vitaceae) until the reddish flowers with
their odour of rotting flesh break through. Rafflesia arnoldii R. Br. has the largest single flower known
in the plant kingdom (up to 1 m across). The plants are bisexual (hermaphrodite), monoecious or
dioecious. The indumentum can be simple, stellate or lepidote. T-shaped unicellular hairs are
characteristic for Malpighiaceae (also called balance hairs, medifixed hairs, or "malpighiaceous"
hairs), and have also been reported for Euphorbiaceae (Argythamnia, Chiropetalum, Rhodothyrsus).
They are, however, also found in other, unrelated families. Stinging hairs of two different types are
found in Euphorbiaceae, and also in Malpighia.
Most flowers are polysymmetric (regular), but the genus Viola, for example, is well-known for its
monosymmetric (zygomorphic) flowers. The perianth in Malpighiales is usually 4 – 5-merous,
consisting of a well-differentiated calyx and corolla (e.g. in Malpighiaceae), or of a single whorl (e.g.
Putranjivaceae). It can also be vestigial (e.g. Salix and Populus) or completely reduced (e.g.
Euphorbia). The calyx of many Malpighiaceae bears oil-producing glands. In some genera of
Euphorbiaceae sensu lato (Dalechampia, Euphorbia, Uapaca), small and inconspicuous flowers are
clustered and subtended by large and more conspicuous bracts. This type of inflorescence, called
pseudanthia, or cyathia in Euphorbia, presents to pollinators the appearance of a single large flower. In
Dalechampia, the bracts secrete resin to attract specialised bees (Armbruster 1984). Some Mabea
species (Euphorbiaceae) from tropical America with large bracts and sturdy inflorescences are
pollinated by birds, marsupials and even monkeys
A floral disc is often but not always present. The androecium is often comprised of 4 – 5 stamens and
is isomerous with the perianth, but the number of stamens varies from one in Euphorbia to c. 1000 in
Ricinus where the filaments are variously united into branching fascicles. Staminodes occur in some
taxa; they can be very conspicuous (e.g. Passiflora and related taxa where they form a corona), and in
some Clusiaceae (Bittrich & Amaral 1996) secrete triterpenoid resins. Euphorbiaceae and Clusiaceae
are the only plant families known so far to attract pollinators by resin secretion from floral structures
(Armbruster 1984).
The gynoecium is syncarpous throughout although in some taxa it is reduced to only one carpel. The
ovary is superior with the exception of some Turneraceae and Homalium in Salicaceae sensu lato
which have semi-inferior ovaries, a few Rhizophoraceae with inferior ovaries, and Dichapetalaceae
which can have superior to inferior ovaries. Placentation in the order is very diverse - the emphasis
laid on this character was one of the major reasons why these families have not been considered to be
closely related in the past. Placentation can be basal, parietal or apical-pendulous; apotropous or
epitropous; orthotropous, hemitropous or anatropous. There are one to many ovules per carpel/locule.
The same diversity is displayed in the fruits: capsules, winged samaras, berries or drupes are all
common. Fruit dispersal is also diverse. There are wind-dispersed winged fruits in Malphigiaceae,
wind-dispersed seeds in Salicaceae, many bird-dispersed drupes and berries, and also mammaldispersed taxa such as the lemur-dispersed Madagascan species of Uapaca in Phyllanthaceae. The
majority of Euphorbiaceae, Phyllanthaceae and Picrodendraceae (all Euphorbiaceae sensu lato) have
unique capsules that forcefully expel the seeds on drying. Humiriaceae are dispersed by water - their
fruits contain resinous cavities enabling them to float down rivers and along coasts.
The seeds bear some of the most significant shared characters for the order, and indeed for the order
and its sister groups. Malpighiales and the two most closely related orders Celastrales and Oxalidales
share exotegmic seeds, although there seem to be exceptions (Tobe & Raven 1988a). In Malpighiales
the exotegmen is often fibrous (e.g. Erythroxylaceae, Malpighiaceae, Pandaceae, Rhizophoraceae,
Violaceae and most Phyllanthaceae), but palisade layers are, for example, found in Euphorbiaceae
sensu stricto, Hypericaceae and Passifloraceae (Corner 1976, Tobe & Raven 1988a). Seeds are often
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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arillate and sometimes winged, and can be albuminous or exalbuminous, with the embryo thin and flat
or folded or fleshy.
Fossil record
The most recent Malpighialean fossil find was an extinct genus of Salicaceae (Pseudosalix) that was
found in an Eocene formation in Utah, USA (Boucher et al. 2003). This twig with attached leaves and
flowers combines typical lanceolate Salix leaves with the branched inflorescences and large sepals of
flacourtiaceous genera such as Idesia, Polyothyrsis and Bennettiodendron.
A well-preserved fossil of flowers of Clusiaceae, Palaeoclusia Crepet & Nixon (1998), from the Late
Cretaceous (c. 90 million years ago), was found in New Jersey. It looks similar to modern Clusioideae,
and shows that the family had already been well-differentiated in that period. An amorphous substance
found in stamens or staminodes is assumed to be sticky resin. Several taxa of modern Clusiaceae
produce triterpenoid resin as a reward for highly specialised bee pollinators (Armbruster 1984, Bittrich
& Amaral 1996). Crepet & Nixon mention other clusioid taxa found in the same deposit which
indicates that the family was already diverse at that time.
Willemstein (1987) listed an entomogamous flower of Antidesma from Baltic Amber. The fossil fruit
Crepetocarpon perkinsii (Dilcher & Manchester 1988) was described from the North American
Eocene and considered most similar to the extant Hippomane (Euphorbioideae). More fossil
euphorbiaceous schizocarps, with both one- and two-seeded locules, and seeds were found in the
Eocene London Clay Flora and the Pipe-Clay Series of Dorset and described as Euphorbiotheca and
Euphorbiospermum species, respectively (Reid & Chandler 1933; Chandler 1962).
Roy & Ghosh (1982) gave numerous references of records of fossil woods of Euphorbiaceae from
around the world. Most of these date from the Tertiary, however, several taxa of Paraphyllanthoxylon
from North America and South Africa, and Bridelioxylon from South Africa have been described from
the Cretaceous. The hard endocarps of the drift fruits of Humiriaceae have repeatedly been found in
tertiary layers. The first find in Colombia was made at an altitude of c. 8000 ft. in Colombia and dated
to Oligocene or Eocene (Cuatrecasas 1961).
In a survey of fossil angiosperm pollen by Muller (1981), the first appearance of several Malpighiales
families was confirmed. The earliest find was that of Ctenolophon from the Upper Cretaceous
(Maestrichtian). Euphorbiaceae sensu stricto and Putranjivaceae were first recorded from the
Palaeocene, Clusiaceae and Phyllanthaceae from Lower Eocene, Caryocaraceae and Malpighiaceae
from Middle Eocene, Rhizophoraceae from Upper Eocene, Salicaceae sensu lato (Casearia) and
Salicaceae sensu stricto from Oligocene, Linaceae from Upper Miocene, and Humiriaceae from
Pliocene layers. Gruas-Cavagnetto & Köhler (1992) cited 12 genera of Euphorbiaceae sensu lato for
the French Eocene, several of which are today restricted to the tropics. Because of their specialised
ecology, fossil pollen of the mangrove genera of Rhizophoraceae have been used as guide fossils
indicating humid tropical lowland climate. In a review of the records of Rhizophora pollen in the
literature, Muller & Caratini (1977) confirmed that specific diversification and even hybridisation had
already happened in Oligo-Miocene sediments in Mexico.
In summary it can be assumed that the lineages representing the recent families of Malpighiales
diverged in the Cretaceous, about 100 million years ago. This process was likely to have been a rapid
diversification judged from the short branches at the base of the order found in the molecular analyses
(Davis et al. 2005).
The families of Malpighiales
The individual families constituting Malpighiales are discussed below in more detail, starting with the
traditional families Euphorbiaceae sensu lato and Flacourtiaceae, and followed by clades roughly
arranged in order of size. The table gives an overview over some data for each family, arranged
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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alphabetically. Information taken from Mabberley (1997), Watson & Dallwitz (1992), and Stevens
(2001) is not always acknowledged in detail as this would have rendered the text impossible to read instead a general acknowledgement of these invaluable sources of information is given here.
Euphorbiaceae sensu lato (Centroplacaceae, Euphorbiaceae sensu stricto, Pandaceae,
Phyllanthaceae, Picrodendraceae, Putranjivaceae): The largest group of Malpighiales both in
number of genera and number of species is Euphorbiaceae sensu lato (the spurge family).
Centroplacaceae, Pandaceae, Phyllanthaceae, Picrodendraceae and Putranjivaceae are all segregates of
Euphorbiaceae. They have been treated as part of this family by most authors to date (e.g., Webster
1994, Radcliffe-Smith 2001). Molecular evidence for monophyly of these lineages, however, has not
been found. Euphorbiaceae sensu lato and Flacourtiaceae (see below) are among the few traditionally
recognised angiosperm families that could not be proven to be monophyletic in the course of the
higher-level molecular studies.
Molecular scientists hold that the individual lineages of Euphorbiaceae sensu lato show such a high
degree of genetic divergence that they represent phylogenetic lineages equivalent to families, and
should therefore be taxonomically recognised as such. Chase & al. (2000) argue against the use of
single key characters and for consideration of divergence of the entire genome as main criterion for
family delimitation, even if this results in morphologically less recognisable units.
Three of the clades found in molecular analyses are more or less congruent with major suprageneric
taxa in the current classification of Euphorbiaceae (Webster 1994, Radcliffe-Smith 2001):
Euphorbiaceae sensu stricto includes the uniovulate subfamilies Acalyphoideae, Crotonoideae and
Euphorbioideae; Phyllanthaceae is equivalent to the biovulate subfamily Phyllanthoideae (minus
Putranjivaceae, see below), whereas the other biovulate subfamily Oldfieldioideae must for
nomenclatural reasons be called Picrodendraceae when raised to family level.
There are several non-molecular differences between uniovulate (Euphorbiaceae sensu stricto) and
biovulate (Phyllanthaceae and Picrodendraceae) taxa apart from ovule number. The most common
base chromosome number for biovulate taxa is x=13, whereas the uniovulate taxa show base numbers
of x=(7–) 9 (–11) (Hans 1973). Wood anatomy is relatively uniform in the uniovulate taxa but very
diverse in the biovulate taxa (Mennega 1987). The same is true for seed anatomy. The uniovulate taxa
are anatomically uniform and have exotegmic seed coats with a palisade layer. The seeds of the
biovulate taxa are extremely diverse, and the outer mechanical layer is usually fibrous (Corner 1976,
Stuppy 1996).
The explosive capsule with typical dehiscence and persistent columella is a unique character shared by
many taxa of Euphorbiaceae sensu stricto, Phyllanthaceae and Picrodendraceae (Pandaceae and
Putranjivaceae have indehiscent fruits) and has high recognition value in a family generally lacking
striking morphological synapomorphies. Whether the fruit type is plesiomorphic for the three families,
however, cannot be shown by the molecular phylogenetic analyses so far published (Kathriarachchi et
al. 2005, Wurdack et al. 2005) due to poorly supported deep nodes in the trees. Critical taxa such as
Bischofia in Phyllanthaceae and the Peroideae in Euphorbiaceae sensu stricto, have indehiscent or
atypical, non-explosive fruits. A parallel origin of this structure in different euphorbiaceous lineages
cannot be excluded.
Euphorbiaceae sensu stricto are best known by the genus Euphorbia, the spurge. With over 2000
species, Euphorbia is one of the five largest plant genera. It is the type genus of the subfamily
Euphorbioideae which always has white, caustic latex. Tribe Euphorbieae is characterised by
specialised pseudanthial synflorescences called "cyathia" (singular: cyathium) consisting of bracts
subtending 4 – 5 staminate inflorescences (reduced to a single stamen), and a terminal pistillate flower
(reduced to a gynoecium). Many herbaceous species of temperate regions are well-known garden
weeds, whereas many succulent taxa (mainly) from Africa and Madagascar are horticulturally
desirable, and often highly threatened by illegal collecting. Many of these species are spiny,
superficially resembling cacti which are nearly absent in the Old World. Euphorbia pulcherrima
Willd. ex Klotzsch from Mexico is a popular house plant (poinsettia). The only other Euphorbiaceae
genus native to Britain and northern and western Europe is Mercurialis. Mercurialis perennis (dog’s
Petra Hoffmann
© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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mercury) is a poisonous plant growing in shady forest undergrowth, whereas the less poisonous M.
annua (annual mercury) is a common weed of wastelands and cultivated areas (introduced in
America).
Manihot esculenta Crantz (cassava, manioc, tapioca or yuca) is the fourth most important food plant in
the tropics. This starch crop of neotropical origin is known to have been in cultivation by 2000 B.C. It
grows in poor, dry soils and is nearly immune to locust attack. The starchy, tuberous roots contain
HCN which is removed by correct preparation. Another member of the subfamily Crotonoideae is
Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg., the rubber tree. It originated in the Amazon basin.
In 1873 the English forester Henry Wickham brought 70,000 seeds from Brazil to Kew Gardens in
England to be germinated. From there they were shipped to South-East Asia which is now the main
centre of cultivation. Natural rubber has played a major role in the industrial revolution, and still
accounts for c. 1/3 of the world's consumption of tyres and tyre accessories.
Ricinus communis L., the castor oil plant is grown as a source of oil. The seeds were found in Egyptian
tombs dated 4000 B.C. The seed oil was probably used as an illuminant and unguent, later medicinally
as a purgative, but is also an excellent industrial lubricant. The oil is free of the water-soluble
compound ricin, a compound highly toxic to animal and man, which has recently made news headlines
in connection with terrorist threats. The generic name compares the carunculate seeds with sheep-ticks
(Latin: ricinus). The plant is sometimes grown as an ornamental in Europe. Euphorbiaceae are also
notable in the secretion of resin from floral bracts in Dalechampia (Armbruster 1984), and the
presence of stinging hairs in different taxa (e.g., Cnidoscolus, Tragia).
Phyllanthaceae (previously Euphorbiaceae-Phyllanthoideae) have small and inconspicuous flowers
standing in axillary fascicles or in racemes. The main morphological difference from Euphorbiaceae
sensu stricto is the presence of two ovules in each locule of the ovary (as opposed to one in
Euphorbiaceae sensu stricto). They have no latex, and with very few exceptions alternate, simple,
entire leaves. Phyllanthus is a large and diverse pantropical genus of c. 1200 species. It's scientific
name means "the flowering leaf", and probably relates to groups of leafless species in the West Indies
and South America with flattened green shoots (phylloclades) at the margins of which flowers and
fruits arise. Most other species bear their leaves on specialised lateral shoots resembling compound
leaves ("phyllanthoid branching"). Phyllanthus emblica L. (emblic, nelli or Indian gooseberry) and
Phyllanthus acidus (L.) Skeels (Otaheite gooseberry) are grown for their vitamin C rich, edible fruits.
Other phyllanthoid genera with fleshy edible fruits include Antidesma, Baccaurea and Uapaca.
Similar obligate pollination mutualism with the same genus of seed-consuming moths have been
reported in species of New Caledonian Phyllanthus (Kawakita and Kato 2004a) as in Asian
Glochidion (Kato et al. 2003) and Breynia (Kawakita and Kato 2004b). Both Breynia and Glochidion
are deeply embedded in Phyllanthus sensu lato and should therefore be subsumed in that genus.
Comparable pollination syndromes are otherwise only known in Ficus (Moraceae) and Yucca
(Agavaceae) which are pollinated exclusively by seed-parasitic wasps and moths, respectively.
The monotypic genus Centroplacus has recently been recognised as family Centroplacaceae (Doweld
2005) after having been excluded from other euphorbiaceous lineages (Wurdack et al. 2004) and
placed isolated in Malpighiales. The West African Centroplacus glaucinus is a non-descript plant with
small flowers in branched inflorescences. The biovulate plant with carunculate seeds differs from other
biovulate lineages by its lack of an obturator.
Picrodendraceae (previously Euphorbiaceae-Oldfieldioideae) are also biovulate, and have been
recognised as a separate taxon from Phyllanthaceae only as recently as 1967. This segregation was
based on differences in pollen morphology: Picrodendraceae have echinate pollen whereas
Phyllanthaceae have predominantly smooth to reticulate pollen. There are no consistent distinguishing
macromorphological characters between the two groups, but Picrodendraceae contain a number of taxa
with compound leaves, a character limited in the Phyllanthaceae to Bischofia javanica Blume.
Hyaenanche globosa (Gaertn.) Lamb. & Vahl from South Africa produces a toxin (Hyaenanchin)
which is used to poison hyaenas (hence the name). Phyllanthaceae and Picrodendraceae are weakly
monophyletic (Wurdack and Davis unpublished manuscript).
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© Royal Botanic Gardens, Kew
8 Oct. 2003, updated 6 Sept. 2005
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The small palaeotropical family Pandaceae (not to be confused with the monocotyledonous family
Pandanaceae) has been variously assigned to Euphorbiaceae-Acalyphoideae as tribe Galearieae
(Webster 1994, Radcliffe-Smith 2001), or regarded as a separate family (Forman 1966). The pseudopinnate appearance of the shoots had led to placement of members of this family in Burseraceae,
Sapindaceae and Anacardiaceae. The main morphological differences of Pandaceae from
Euphorbiaceae sensu stricto are the orthotropous ovules of the monotypic genus Panda, the divergent
anatomy of the nodes and the absence of an obturator. Panda oleosa Pierre has large seeds dispersed
exclusively by elephants. The seed oil is used locally in cooking.
The position of Drypetes and Putranjiva in Euphorbiaceae-Phyllanthoideae-Drypeteae has not been
questioned for the longest time, mainly because their morphological characters can easily be
accomodated within diverse Phyllanthaceae. However, molecular studies have excluded this
palaeotropical group from the Phyllanthaceae as Putranjivaceae. Non-molecular evidence comes from
caryology (base chromosome base number x=13 in Phyllanthoideae, x=10 in Drypetes; Hans 1973),
presence of mustard oil glycosides which are unknown outside Brassicales (Rodman et al. 1996) as
well as ovule ontogeny and structure (Meeuse 1990). Putranjivaceae do not possess the typical
euphorbiaceous schizocarps but have drupes. They also have a central staminate disc which is rare in
Phyllanthaceae. Drypetes is often recognised by its shiny leathery leaves which can be spiny at the
margin.
Salicaceae sensu lato and Achariaceae sensu lato (including Flacourtiaceae): Flacourtiaceae, like
Euphorbiaceae, were always notoriously difficult to recognise at family level. One of the most highly
acclaimed field botanists, Al Gentry (1993), described these groups as "infamous as one of the most
variable families vegetatively: if you can't figure out what [a plant] is, try Euphorbiaceae (or
Flacourtiaceae)". Both families have for this reason developed into "dustbin families", and were found
in DNA sequence analysis to be heterogeneous.
Flacourtiaceae, characterized mainly by their parietal placentation, fell into several clades widely
distributed in the angiosperms (e.g., Soltis & al. 2000, Chase et al. 2002). The genus Berberidopsis is
now recognised as a separate family, Berberidopsidaceae, and together with Aextoxicaceae (which in
some classifications had been considered close to Euphorbiaceae) forms the order Berberidopsidales at
the base of the core eudicots. The monotypic genus Aphloia was also given family status, as
Aphloiaceae, and is found at the base of the rosid clade. Muntingia was shown to be a member of
Malvales and has now been assigned to the new family Muntingiaceae in that order. All other
Flacourtiaceae belong to Malpighiales. They fall into two distinct, well-supported clades, Achariaceae
sensu lato and Salicaceae sensu lato.
The first clade (which excludes Flacourtia, the type genus of Flacourtiaceae) is distinguished partly by
the presence of cyanogenic glycosides and the lack of salicoid teeth. It has embedded within it the
Achariaceae, a South African family of three genera and four species (Chase & al. 2002). The name
Achariaceae is conserved and must therefore be adopted for this clade. The second clade, which
includes Flacourtia, has embedded within it the family Salicaceae sensu stricto (i.e. the mainly
northern temperate genera Salix and Populus) and it is from this family that it takes its name.
The wind-pollinated Populus (poplar) is an important timber, mainly used for the production of pulp,
matches, veneer etc. The wood is relatively soft but the trees are extremely fast-growing. The seeds
have conspicuous long white hairs (cottonwood). The c. 400 species of the genus Salix (willows) are
usually insect-pollinated. Several creeping species are an important element of arctic and alpine floras.
Salicin extracted from willow bark is the origin of the pain and fever relief today synthesized as aspirin
(acetylsalicylic acid). Willows are widely planted for erosion control and land reclamation. Many
species are cultivated as ornamental trees and shrubs, and the pliable branches (called withies or
withes) are used for basket weaving. The timber is used, e.g., for Dutch clogs and cricket bats.
Clusiaceae, Hypericaceae, Bonnetiaceae and Podostemaceae: These families form a highly
supported clade in molecular phylogenetic analyses.
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Clusiaceae is also called Guttiferae - it is one of the few plant groups with an alternative name
(normally the nomenclatural rules allow only one name for each plant taxon). This tropical family can
be recognised by its usually bright yellow or orange latex and its numerous anthers. The genus Clusia
shows a great diversity of pollination mechanisms and androecial differentiation although the pistillate
flowers can be very uniform. This phenomenon may be at least partly explained by the production of
sticky triterpenoid resin in the androecium as a reward for highly specialised bee pollinators. This
necessitates a spacial separation between resin and pollen (Bittrich & Amaral 1996). Many taxa in the
group have characteristic large, flat, spreading or even umbraculiform stigmas. For an interesting fossil
of Clusiaceae, see under Fossil evidence. The family was previously classified in the order Theales
(APG classification now places Theaceae in Ericales).
One of the most highly valued tropical fruits is the mangosteen, Garcinia mangostana L. Originating
and grown almost exclusively in the humid lowlands of South East Asia, the sweet and juicy white
arils surrounding the seeds contained in the shiny, dark purple fruits are a delicacy. The trees,
however, are slow growing, the seeds have a very long germination period and vegetative propagation
is difficult. For these reasons, mangosteen is a relatively expensive fruit even where it is grown.
Hypericaceae is not widely recognised as a separate family but usually treated as the first subfamily
Hypericoideae of Clusiaceae sensu lato (e.g., Seetharam 1985, Gustafson et al. 2002). It is
characterized by the combination of 3 or 5 styles and opposite leaves bearing pellucid gland dots. The
largest genus by far (c. 370 species) is Hypericum (St. John's wort) which occurs in temperate regions
and on tropical mountains. Some Hypericum species with rather large, bright yellow flowers are
cultivated as ornamentals, and extracts from Hypericum perforatum L. are widely used as an antidepressant. The leaves of the Afro-malagasy species Harungana madagascariensis Lam. are
medicinally used against skin diseases. The predominantly neotropical Bonnetiaceae (only the genus
Ploiarium is palaeotropic) are also often treated as a subfamily of Clusiaceae sensu lato, i.e.
Bonnetioideae.
Podostemaceae, on the other hand, have in the past been placed in a monotypic order and associated
with a variety of completely unrelated families. This is not surprising considering the extreme
adaptation of these plants to an aquatic lifestyle. They are herbs of very peculiar form (thalloid),
resembling lichens, mosses or sea-weed, and growing usually submerged on rocks in rivers. The recent
association with Clusiaceae/Hypericaceae had never been considered before and is a good example of
the power of molecular analysis to detect natural relationships amongst highly modified organisms.
Malpighiaceae: Once considered to be close to Polygalaceae (Fabales), this is now the type of
Malpighiales, i.e. the family from which the order takes its name. Malpighiaceae include c. 1250
species, 85% of which are neotropical. Malpighiaceae are shrubs, small trees or lianas, and can often
be recognised by their T-shaped unicellular hairs ("malpighiaceous hairs"). They have fairly uniform
bisexual pentamerous flowers with clawed, often fringed, usually yellow petals, ten stamens and three
carpels. Fruit morphology, on the other hand, is very diverse, including bristly and variously winged
fruits. Most American genera have floral oil-glands (calyx glands) that produce rewards for specialised
pollinators, namely oil-gathering bees. These bees do not occur outside America, and the Old World
taxa of Malpighiaceae either lack the calyx glands, or their calyx glands produce sugary nectar which
attracts non-specialised pollinators. Banisteriopsis caapi (Spruce ex Griseb.) C.V. Morton
contains harmaline (harmidine) alkaloids. This South American vine (Ayahuasca, Yagé,
Caapi) has hallucinogenic properties and is used in traditional shamanic healing. Malpighia
glabra L. produces edible fruits (Barbados cherry, acerola). More general information on the family
can be found in Anderson (1990), Cameron & al. (2001), Davis and Chase (2004) and Davis & al.
(2001).
Violaceae, Passifloraceae, Malesherbiaceae, Turneraceae: Violaceae or the violet family is well
known for its only temperate genus Viola. The c. 400 species of Viola, making up about half of the
family, include herbs and (rarely) subshrubs with conspicuous zygomorphic, frequently cleistogamous
flowers. The anterior petal is often spurred and contains nectar. The seeds are dispersed by ants which
are attracted by the oily appendices of the seed. Over 120 species of Viola are grown as ornamentals
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(violets, violas, pansies). Because of the association with herbaceous violets, the woody (sometimes
climbing), tropical taxa of Violaceae are often not easily recognised as members of the family. Key
characters are a single style, syncarpous ovaries with only one locule and parietal placentation. The
leaves are often serrate and the fruits dehiscent and 3-valved. The largest woody genus is Rinorea with
c. 200 species.
Passifloraceae are easily the family with the largest and most showy flowers in the order. They are
usually climbers with alternate leaves, axillary tendrils and simple (entire or palmately lobed) or
palmately compound leaves which usually have nectaries at the top of the petiole. The flowers are
regular and usually bisexual, and possess a conspicuous corona of one or more rows of staminodes
around the androecium. An androphore or an androgynophore is frequently present. The superior,
syncarpous ovary is one-locular, with parietal placentation.
The principal genus in Passifloraceae is Passiflora with c. 400 species. The name 'passion flower' was
coined by Catholic missionaries in South America in reference to Christ's crucifixation, with the
tendrils representing whips and the corona the crown of thorns (Mabberley 1997). Many species of
Passiflora are cultivated as ornamentals and the fruits of several species (e.g. passionfruit, granadilla
and maracuja) are widely grown. The yellow or purple berries contain seeds surrounded by juicy
acidic-tasting arils. Cultivation is mainly for the juice and for flavouring desserts such as ice cream and
yoghurt, but fruits are also produced for raw consumption. The second largest genus of the family,
Adenia or desert rose, has about 100 species which are distributed mainly in dry areas of Africa and
Madagascar. Most species are odd-looking succulents with a swollen base of the trunk, and thorny,
wiry, vining, often leafless branches. The inconspicuous flowers are dioecious.
Malesherbiaceae and Turneraceae are most closely related to Passifloraceae (Davis and Chase 2004,
Wurdack and Davis unpublished manuscript). The two families have alternate leaves with glandular
hairs exuding an unpleasant smell. The flowers are regular and pentamerous; calyx and corolla
together form a long tube, the free parts of which are either contorted (Turneraceae) or valvate
(Malesherbiacae). Both families have one-locular syncarpous ovaries and parietal placentation,
characters shared with Passifloraceae. Turneraceae occur in America and Africa to Madagascar and
Rodriguez Island. They have arillate seeds, and frequently have extrafloral nectaries at the top of the
petiole, as in Passifloraceae. A molecular phylogenetic analysis of the principal genus Turnera
explored complex patterns of chromosome number evolution including numerous instances of
polyploidy, and the distribution of homostyly and heterostyly (Truyens et al. 2005). Malesherbiaceae
include only Malesherbia, a small genus of herbs and subshrubs restricted to temperate (Andean)
South America. The floral tube is persistent in fruit, and the long, slender styles are inserted
subapically. Like Passifloraceae, Malesherbiaceae develop androgynophores, but differ from both
Passifloraceae and Turneraceae in their exarillate seeds.
Chrysobalanaceae, Euphroniaceae, Dichapetalaceae, Trigoniaceae and Balanopaceae. Another
very strongly supported clade within Malipighiales consists of Chrysobalanaceae, Dichapetalaceae,
Euphroniaceae, and Trigoniaceae. A relationship between Chrysobalanaceae and the other families in
this clade, or indeed in the Malpighiales, had previously not been suggested. Although Prance & White
(1988) argued for family status for Chrysobalanaceae (which frequently had been included in
Rosaceae), they retained it in the order Rosales due to lack of conclusive evidence for a more
convincing placement. Chrysobalanaceae are pantropical and particularly species-rich in the
neotropics.
Chrysobalanaceae are woody plants with alternate, simple, usually entire leaves, often with foliar or
petiolar glands. Floral characters include a gynobasic style, an often asymmetrical gynoecium, basal
placentation, an erect ovule and embryo, and a tendency towards zygomorphy. The fruits are
indehiscent, fleshy drupes sometimes with a hairy endocarp. The Australian genus Stylobasium,
excluded from the family by Prance & White (1988), is now placed in Surianaceae in Fabales (Soltis
& al. 2000). Affinity of the other excluded genus, Rhabdodendron, with Caryophyllales was also
confirmed by molecular studies. It is sister to the all other Caryophyllales (Savolainen & al. 2000,
Soltis & al. 2000).
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Dichapetalaceae are trees, shrubs or lianas which are usually very poisonous due to fluoroacetic acid
and pyridine alkaloids. The plants are especially dangerous to lifestock in southern Africa where they
are known as "gifblaar" or "poison leaf" and cause the condition known as dichapetalosis. The
inflorescences are often epiphyllous, i.e. inserted on the petiole. Dichapetalaceae have been associated
with Euphorbiaceae sensu lato, probably because of the two pendulous, anatropous and epitropous
ovules per locule. The fruits are one-seeded drupes.
Trigoniaceae stand out by their more or less papilionoid flowers and their disjunct distribution.
Trigonia and Trigoniodendron are found in Central and/or South America; Trigoniastrum is a
monotypic genus of Western Malesia, and Humbertiodendron is likewise monotypic and endemic to
Madagascar. The leaves are usually opposite (alternate only in Trigoniastrum), and the flowers are
sometimes spurred.
Euphroniaceae, comprising only the small genus Euphronia, have a distinctive androecium consisting
of four fertile stamens in two opposite pairs, separated on one side by a long staminode with a sterile
anther, and on the other side by one to five short denticulate staminodes. Euphronia has been placed in
Vochysiaceae and Trigoniaceae in the past (APG placement of Vochysiaceae is in Myrtales). It was
given family rank for the first time in 1989 - a decision that was confirmed by molecular data (Litt &
Chase 1999). All species are endemic to the Guayana Shield (Steyermark & Marcano-Berti 1999).
Sister to this clade is the enigmatic family Balanopaceae. It consists of the single genus Balanops
distributed mainly in New Caledonia, but also in Queensland and the SW Pacific. The plants are
anemophilous with a reduced perianth and the staminate flowers in catkins. The drupaceous fruits are
subtended by numerous crowded bracts resembling acorns. For this reason, Balanopaceae have
sometimes placed in the order Fagales. Balanops has been monographed by Carlquist (1980).
Ochnaceae sensu lato incl. Quiinaceae and Medusagynaceae: Ochnaceae is a tropical family
particularly diverse in Brazil. The family is morphologically heterogeneous, and several segregate
families have been recognised in the past. It has been comprehensively treated by Amaral (1991). A
good diagnostic character are the many parallel leaf-veins, although this is also found in many
Clusiaceae (but Ochnaceae have no latex). The flowers are regular, bisexual, with an equal number of
sepals and petals, the latter frequently yellow or white. The 3 – 8-locular ovary is often distinctive,
with the style apparently arising between the carpels (gynobasic), and the carpels apparently free. It is,
however, truly syncarpous. Synapomorpies of Ochnaceae include the characteristic cristarque cells in
the leaves and the frequently poricidal anthers.
The genera can be grouped into two subfamilies, Ochnoideae (including Lophiraceae) and
Sauvagesoideae (including Sauvagesiaceae, Luxemburgiaceae and Wallaceaceae) which differ in
presence or absence of endosperm in the mature seed, and in seed coat anatomical characters. The
monotypic Madagascan genus Diegodendron was included in Ochnaceae until Amaral (1991)
excluded it. Molecular analysis places it near Bixaceae in the Malvales (Fay & al. 1998). Another
genus excluded by Amaral is Strasburgeria, a monotypic genus from New Caledonia. This was found
by rbcL sequence data to be sister to Ixerba and closely related to Crossomatales (Savolainen & al.
2000). Scytopetalaceae, thought to be close to Ochnaceae, is now part of Lecythidaceae.
Quiinaceae have always be considered to be close to Ochnaceae, and this has been confirmed by
molecular data. The small neotropical family differs in the opposite (or whorled leaves) which have
similarly close and numerous secondary veins, and which can be pinnate (usually simple in
Ochnaceae).
The relationships of the monotypic family Medusagynaceae have been relatively obscure. The single
species Medusagyne oppositifolia Baker is endemic to the island of Mahé (Seychelles) where it is very
rare and highly endangered. It is called jellyfish tree or bois méduse. This refers to the peculiar fruit
which has carpels that open septicidally from the base. The c. 20 carpels diverge from a central column
like the spokes of an opening umbrella, or like a gorgon's head, each crowned by a free, capitate
stigma. This dehiscence is more spectacular but similar to some Ochnaceae, as are aspects of seed
morphology, whereas the absence of stipules distinguishes the family from both Ochnaceae and
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Quiinaceae. The clade comprising Ochnaceae, Quiinaceae and Medusagynaceae received 99%
bootstrap support (Fay & al. 1997).
Erythroxylaceae and Rhizophoraceae: Erythroxylaceae are a family of small trees and shrubs with
inconspicuous, regular, pentamerous flowers. The perianth is differentiated into calyx and corolla, and
the petals are internally ligulate. There are 10 stamens and a superior, tricarpellate ovary maturing into
a fleshy drupe with usually only one fertile locule, and a single seed per locule. The branches are often
covered with distichous scales representing vestigial leaves. The leaves are entire and usually
alternate; they have interpetiolar or (in Erythroxylum itself) intrapetiolar stipules.
The principal genus Erythroxylum accounts for c. 250 of the c. 260 species in the family. It is
pantropical but particularly species-rich in America and Madagascar. The genus contains alkaloids and
has medicinal properties, the most famous species being the coca plant, Erythroxylum coca. The leaves
of this plant are mixed with lime and chewed by South American Indians to suppress hunger and to
maintain strength under harsh climatic conditions and a poor diet. Coca leaves are also used as
infusions and in poultices. The alkaloid cocaine extracted from the plant acts as a strong stimulant and
aphrodisiac. It is a high-profile illegal and addictive drug distributed in large quantities worldwide by
drug cartels.
Rhizophoraceae are generally known as plants of the mangrove. This is true only for tribe
Rhizophoreae which includes four genera (e.g. Rhizophora) with conspicuous aerial roots and
viviparous seeds. These seeds germinate while still on the mother-plant, developing a substantial
radicle which allows them to root as soon as they are dropped into the water. It is less well-known that
all other taxa, such as the genus Cassipourea, occur inland.
Rhizophoraceae always have opposite (or verticillate) leaves with interpetiolar stipules. The petals are
fringed in all but two genera. They enclose either a single antipetalous stamen or a group of 2 – 6
stamens. This character is otherwise only known from Rhamnaceae, a family which differs in many
other respects and can hardly be confused with Rhizophoraceae. The ovary in Rhizophoraceae can be
superior to inferior, the latter being a rare and derived condition in the family (Juncosa & Tomlinson
1988a, also giving a taxonomic overview over Rhizophoraceae). Some species yield wood used for
underwater construction and piling, and tannins are obtained from the bark.
The systematic position of Rhizophoraceae has been highly debated and was the subject of a
symposium held in Amherst (Mass., USA) in 1986. In conclusion, the four genera of the aberrant tribe
Anisophylleae with alternate leaves were recognised as family Anisophyllaceae on the basis of general
morphology (Juncosa & Tomlinson 1988b), pollen morpology (Vezey & al. 1988), embryology (Tobe
& Raven 1988b) and sieve-element plastids (Behnke 1988). Seed morphology allied Rhizophoraceae
to Elaeocarpaceae and Celastraceae (Tobe & Raven 1988a), now placed in the related orders
Oxalidales and Celastrales respectively. Sieve-element plastids associated Rhizophoraceae with
Humiriaceae and Erythroxylaceae of Malpighiales (Behnke 1988). As a consensus, these families, as
well as Linaceae, Lepidobotryaceae and Oxalidaceae were listed as the closest relatives to
Rhizophoraceae (Dahlgren 1988) - a placement very near to those in the molecular analyses
(Setoguchi et al. 1999, Schwarzbach & Ricklefs 2000). Erythroxylaceae and Rhizophoraceae are so
closely related that they could be united as one family. Another non-molecular character supporting
this is the presence of colleters in both families (Thiebaut and Hoffmann 2005). Anisophylleaceae
belongs to Cucurbitales (Savolainen & al. 2000).
Linaceae (including Hugoniaceae): This family consists of trees, lianas, shrubs and herbs, all with
entire leaves and bisexual flowers. The frequently assumed close relatioship between Linaceae sensu
stricto and Hugoniaceae has been confirmed by molecular studies (Savolainen & al. 2000). They are
sister groups and should be recognised as subfamilies Linoideae and Hugonoideae. Linoideae are
herbs or shrubs (rarely trees) with alternate to opposite, sessile leaves, whereas Hugonioideae are
lianas with alternate leaves. Linoideae are mainly northern temperate and subtropical, whereas
Hugonioideae are pantropical.
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The largest genus is Linum (flax) with c. 200 species. The flowers are red, yellow, blue or white, often
with contrasting marks at the base of the petals. Linum usitatissimum L. (common flax) is an important
fibre and oil plant. The stems are the source of linen, canvas, twine and other products. The seeds yield
linseed oil which is used in paint and varnish, soap and in food processing. The oil can be consumed
but not used in cooking as it becomes toxic when heated. The seeds are traded as a dietary supplement
(as a source of alpha-linolenic acid and against constipation). Dried and ground linseed oil is the main
component of linoleum, the original flexible flooring. It is now widely replaced by vinyl (PVC) which
is a petroleum product, although the natural product has many advantages. Some Linum species are
grown for their ornamental value.
Humiriaceae are woody plants with alternate simple leaves and bisexual petaliferous flowers with an
intrastaminal disc and superior ovary. The anthers have thick, fleshy connectives. The family is
notable for its bouyant drift fruits. These contain empty resinous cavities which enable the fruits to
disperse along rivers and coasts. Only one species is found outside America; it occurs on the West
African coast and probably reached this outpost by drifting in ocean currents. The family has been
associated with Linaceae in the past. A complete family revision was published by Cuatrecasas (1961).
The two genera of Elatinaceae, Bergia and Elatine, are plants of moist and wet habitats such as
swamps and lakesides. They are ground-rooted, with decussate or whorled leaves either submerged or
emergent. They were found to be sister to Malpighiaceae (Davis and Chase 2004).
Caryocaraceae are a neotropical family comprising the two genera Caryocar (with opposite
trifoliolate leaves) and Anthodiscus (with alternate trifoliolate leaves). Both genera have large,
bisexual, actinomorphic flowers bearing 50 – 750 stamens. Caryocar villosum Pers. is bat-pollinated.
The fruit mesocarp and the cotyledons of Caryocaraceae are either edible (Caryocar nuciferum L. is
cultivated for its edible 'butter nuts') or poisonous. Prance and Da Silva (1973) have monographed the
family for Flora Neotropica. Caryocaraceae have traditionally been allied to Theaceae and
Ternstroemiaceae (Ericales).
Ixonanthaceae are a tropical family of trees and shrubs with bisexual actinomorphic flowers. The
leaves are spirally arranged and entire to toothed. They have imbricated to contorted petals, and styles
and stamens that are folded in bud. The 1 or 2 pendulous, anatropous ovules per locule with apicalaxile placentation and an obturator are similar to those of Linaceae and Euphorbiaceae sensu lato, but
as in many other Malpighiales families even the analysis of eight loci does not result in a supported
sister-relationship (Wurdack and Davis unpublished manuscript).
Rafflesiaceae: This family is an extreme example of a highly modified organism. They are nonphotosynthetic stem and root parasites living entirely inside the host trees (Tetrastigma in the
Vitaceae) until the reddish flowers with an odour of rotting flesh break through. Rafflesia arnoldii
forms the largest single flower known in the plant kingdom (up to 1 m across). Rafflesiaceae is one of
the last families to be placed within an angiosperm order, but it still lacks supported sister relationships
(Wurdack & Davis unpublished manuscript). Due to its lack of chloroplasts, DNA analysis has to rely
on the mitochondrial genome. There have been reports of horizontal (host-to-parasite) gene transfer of
mitochondrial genes (Davis & Wurdack 2004, Nickrent et al. 2004).
Lacistemataceae includes two small genera from tropical America, Lacistema and Louzania. The
peculiar androecium, situated on one side of the ovary, consists of just one stamen with widely
separated thecae. The fruits are deshicent, one-seeded capsules.
Irvingiaceae are all tall African hardwood trees (only one species in Malesia - Irvingia malayana)
with valuable timber and edible seeds. Irvingia gabonensis Baill. seeds - the bush mango or dika nut,
is a highly desirable forest product. The seeds are pounded and used to thicken soups, or to make dika
bread (Gabon). In Cameroon, temporary villages are set up in anticipation of the ripening of the fruits.
Also included in Irvingiaceae is Desbordesia glaucescens Tiegh., one of the tallest trees of the West
African forest (50 – 60 m). This monotypic species develops wide buttresses between which the trunk
rots away, a person can easily walk through the gap that is left. Desbordesia glaucescens also has a
samara whereas the fruits all other members of the family are fleshy. All three genera of Irvingiaceae
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share the characteristic large, deciduous intrapetiolar stipules that enclose the terminal bud and leave a
circular scar running around the axis, similar to those in Ficus (Moraceae). This character is found also
in Pseudagrostistachys (Euphorbiaceae sensu stricto). Irvingiaceae have been regarded as members or
close allies of Simaroubaceae (Sapindales).
Ctenolophonaceae have three species in the only genus Ctenolophon, one in tropical Africa and two
in Malesia. The plants produce a sticky, resinous exudate, have a stellate indumentum and entire,
opposite leaves. The flowers are pentamerous with ten stamens, the anthers of which have thick
connectives. Ctenolophon has previously been regarded as a genus of Linaceae, however, according to
molecular studies (Savolainen & al. 2000, Soltis & al. 2000, Wurdack and Davis unpublished
manuscript) it is not closely related to Linaceae.
The monotypic families Goupiaceae and Lophopyxidaceae as well as the genus Bhesa have been
included in Celastraceae (Celastrales) but represent distinct lineages in Malpighiales. Goupia glabra
Aubl. is an important timber tree in Guyana and is used to make dug-out canoes. Malesian Lophopyxis
is highly supported as sister to Putranjivaceae (see under Euphorbiaceae sensu lato).
Acknowledgements:
The information shared by Martin Cheek, Wolfgang Stuppy and Sue Zmarzty is gratefully
acknowledged; Sue Zmarzty also proof-read this article and made many valuable suggestions.
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