4. Euphorbioideae Burnett

Laticifers not articulated, starch grains much elaborated?; staminate flowers: A not covered by P, disc usu. 0; outer
 integument 3-6 or 8-22 cells across, inner integument 3-5(-22) cells across; seeds carunculate or not.

Euphorbia (2420: pseudanthia, many arillate/carunculate, inc. Chamaesyce, Pedilanthus, Monadenium, Synadenium, etc., 
the whole of the Euphorbiinae of Webster 1994b: in Pedilanthus infl. monosymmetric; glands fused commissural stipules: 
see Steinmann & Porter 2002 and Bruyns et al. 2006 - African taxa, the succulents, cf. Park & Elisens 2000; Yang & Berry 2007, 
subgenus Chamaesyce; Park & Jansen 2007: subgenus Esula sister to The Rest, latter only moderate support), Mabea (40). 
Pantropical, extending (mostly Euphorbia) into temperate regions.

Synonymy: Bertyaceae J. Agardh, Hippomanaceae J. Agardh, Ricinaceae Martynov, Ricinocarpaceae (Mller Argoviensis) Hurusawa,
 Tithymalaceae Ventenat, Tragiaceae Rafinesque

    * Euphorbiaceae may be recognised by the leaves on the one branch often being variable in size and/or shape, their
 secondary veins are often  palmate, the margins are toothed, and there are sometimes glands of various kinds. Cauline 
stipules are common, as is latex (the latter not in Acalyphoideae). The plants are mono- or dioecious, the flowers are small
the perianth usually inconspicuous, there are usually three carpels with prominent stigmas, and the fruits have a distinctive
and persistent columella, large and often carunculate seeds (one per loculus), and explosive dehiscence. Euphorbiaceae are
quite often poisonous.

Euphorbiaceae may have diverged from other Malpighiales in the Cretaceous-late Aptian 
([119.4-]113.8[-110.7]/[105.9-]101.6[-101.1] million years before present: Davis et al. 2005a). 
"Euphorbiaceae" are often the second most abundant family in tropical rainforests in South-East Asia and Africa 
(Gentry 1988). Caterpillars of nymphalid butterflies are quite common on this group (Ehrlich & Raven 1964), while those 
of the spectacular Uraniinae moths can be found on Endospermum, Omphalea and Suregada throughout the tropics (Lees & Smith 
1991); the first two are rather closely related, the position of the last is unclear (Wurdack et al. 2005). It would be 
interesting in this context to clarify both Euphorbiaceae phylogeny and Uraniinae host plant preferences.

Flowers of Euphorbiaceae are generally small, and pseudanthia have evolved more than once. However, the distinctive cyathium
 of Euphorbia seems to have evolved but once (Park & Backlund 2002; Wurdack et al. 2005). In Pedilanthus, previously often 
segregated from Euphorbia, the cyathium is red and monosymmetric; the plant is bird-pollinated. It has been suggested that 
the distinctive cyathial nectariferous glands are commissural stipules (Steinmann & Porter 2002; Bruyns et al. 2006, for a 
phylogeny of Euphorbia). The cyathium seems to be a modified cymose inflorescence with a single, terminal, carpellate flower 
(cf. Jatropha, etc.); details of its development are provided by Prenner and Rudall (2007), although they found that the 
morphological nature of both cyathial glands and petaloid structures was unclear (see also Prenner et al. 2008b). 
Dalechampia of the Acalyphoideae also has remarkable pseudanthia; bees may visit the "flowers" for resin, a very uncommon 
reward in flowering plants (see Armbruster 1996 for details).

Molecular analyses by Wurdack and Chase (2002) and especially Wurdack et al. (2005, see also Tokuoka 2007) suggest that 
substantial changes may be needed in the groupings currently recognised in the family. The beginning of the reclassification 
they suggest is given here, with the interpolation of Rafflesiaceae as suggested by Davis et al. (2007) and the associated 
recognition of Peraceae; the main problem remaining is the circumscription of Crotonoideae.

The branching of the entire plant body of Euphorbia subgenus Chamaesyce can be compared with the branching pattern of the 
inflorescence of other species of Euphorbia. Most of the ca 300 pecies of subgenus Chamaesyce have C4 photosynthesis, and 
the subgenus may have originated in the New World (Yang & Berry 2007).

Cyanogens in Euphorbiaceae s. str. can be derived from nicotinic acid or valine/isoleucine (Seigler 1994); latex and 
cocarcinogens are both apparently restricted to Euphorbioideae and Crotonoideae. Growth patterns show much diversity, 
Euphorbia s. str. (i.e. not including Chamaesyce) alone being hideously variable (Keller 1996); E. alata has spirally 
two-ranked leaves! Prismatic crystals in wood parenchyma and/or ray cells are common, and these also occur in Putranjivaceae 
and Picrodendraceae (Hayden 1994). Mennega (1990) suggested that the subdermal initiation of the inner integument separated 
Euphorbiaceae from other families.

Sutter and Endress (1995) argue for a broadly delimited Euphorbiaceae (inc. both Phyllanthaceae and Putranjivaceae), Huber 
(1991) for a narrower circumscription, with the biovulate taxa being considered to be closer to Linales s. str., while Meeuse
 (1990) also suggested that the family should be split - into eleven families. There is no molecular evidence yet for a 
broadly delimited Euphorbiaceae, yet Euphorbiaceae s. str, Phyllanthaceae and Picrodendraceae all have a similar and rather 
distinctive capsule, etc. (see also Sutter et al. 2006). Takhtajan's (1997) Euphorbianae included Pandaceae and 
Dichapetalaceae, as well as Thymelaeales (now in Malvales) and Aextoxicaceae (Berberidopsidales), but this is clearly a 
group that has little to recommend it.

For information on Euphorbiaceae, Phyllanthaceae and Putranjivaceae, see Webster (1967, 1994a - also other papers in 
Ann. Missouri Bot. Gard. 81. 1994: general), Hegnauer (1966, 1989: chemistry), Hans (1973: chromosomes), Evans and Taylor 
(1983: phorbol esters), Jury et al. (1987: chemistry), Beutler et al. (1989, 1996: chemistry), Tokuoka and Tobe 
(1993: general embryology, 1998: ovules and seeds in Crotonoideae, 2002: ovules and seeds in Euphorbioideae, 2003: ovules 
and seeds in Acalyphoideae), Sutter and Endress (1995), Stuppy (1996: seed anatomy), Hayden and Hayden (2000: wood anatomy 
of Acalyphoideae), Lobreau-Callen et al. (2000: pollen, esp. of Crotonoideae), Radcliffe-Smith and Esser (2001: description 
of genera), Esser (2001: general), Westra and Koek-Noorman (2004: wood end-grain), Mennega (2005: wood anatomy of 
Euphorbioideae), Wurdack et al. 2005 (phylogeny) and Tokuoka (2007: character evolution). For pollen morphology of 
Acalyphoideae s.l., see Nowicke and Takahashi (2002) and references. For a comprehensive checklist and bibliography, 
see Govaerts et al. (2000). I am grateful to Hajo Esser for comments.