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20. Euphorbiaceae

大戟科 da ji ke

Authors: Bingtao Li, Huaxing Qiu, Jin-shuang Ma, Hua Zhu, Michael G. Gilbert, Hans-Joachim (Hajo) Esser, Stefan Dressler, Petra Hoffmann, Lynn J. Gillespie, Maria Vorontsova & Gordon D. McPherson

Euphorbia stracheyi

Credit: Harvard University Herbaria

Trees, shrubs, or herbs, rarely woody or herbaceous lianas, monoecious or dioecious, indumentum of simple, branched, stellate, or gland-tipped hairs, peltate or glandular scales or stinging hairs, latex often present, clear, white, or colored; roots woody, rarely roots tuberous and stems succulent, sometimes spiny. Leaves alternate or opposite, rarely whorled; stipules usually present, often free, sometimes modified into spines or glands, deciduous or persistent; petioles long to short, sometimes with glands at apex or base; leaf blade simple, sometimes palmately lobed, rarely compound, or reduced to scales, margins entire or toothed, sometimes with distinct glands along margin and/or on surface, venation pinnate or palmate. Inflorescences axillary or terminal, flowers in cymes or fascicles, these often arranged along an elongated axis, branched or unbranched, forming a thyrse, in congested heads, or in a flowerlike cyathium with very reduced flowers enclosed within a ± cupular involucre; bracts sometimes petaloid. Flowers unisexual, within same inflorescence or in separate inflorescences, actinomorphic. Sepals (1-)3-6(-8), free or connate into calyx tube, valvate or imbricate, rarely absent (Euphorbia). Petals free, often reduced or absent. Disk present or absent. Male flowers with disk intrastaminal or extrastaminal, entire to dissected. Stamens one to very many, hypogynous; filaments free or connate; anthers 2(-4)-locular, mostly dehiscing longitudinally, rarely transversely or by pores, introrse or extrorse; rudimentary ovary sometimes present. Female flowers rarely with staminodes; ovary superior, (1-)2-5(-20)-locular; placentation axile; ovules 1 or 2 per locule, anatropous or hemitropous; styles free or connate, entire or lobed, or multifid, lobes erect, horizontal or curved; stigma capitate, linear, fimbriate, fan-shaped or pinnatilobate. Fruit typically a capsule elastically dehiscent into 2-valved cocci from a persistent columella, sometimes a berry or drupe. Seeds 1 or 2 per locule; seed coat thin to indurate, sometimes fleshy to form a sarcotesta; caruncle sometimes present; aril sometimes present; endosperm present or absent; embryo straight to curved or folded; cotyledons usually broader than radical. x = 6-14.

Trees, shrubs, or herbs, usually without latex (present in Bischofia); indumentum of simple hairs (branched in Phyllanthus reticulatus), often absent. Leaves alternate, often distichous, sometimes scalelike on main stems; petiole usually short, usually without glands (present in Aporosa); leaf blade simple, margin entire or minutely serrulate (long petioles, 3(-5)-foliolate with toothed margins in Bischofia); venation pinnate, rarely obscurely 3-veined from base. Inflorescences mostly axillary, without visible axis (present in Antidesma, Aporosa, Baccaurea, Bischofia, Richeriella). Male flowers with 2-8 stamens, anthers longitudinally dehiscent (variable in Phyllanthus); female flowers with 2 ovules per locule. Seeds without caruncle, sometimes with fleshy aril or fleshy testa.

Trees to shrubs. Leaf blade leathery, grayish when dry, base often asymmetrical. Ovules 1 per locule; stigmas dilated, peltate or reniform. Fruit a relatively large 1-seeded drupe, usually crowned by persistent flaplike stigmas. Seeds without caruncle.

Plants with or without latex; indumentum of simple, stellate, scalelike, stinging, or glandular hairs, sometimes absent. Leaves alternate or opposite; leaf blade simple or compound, sometimes deeply divided, margin entire or variously toothed, often with sessile glands near junction with petiole and/or along margins; venation pinnate or palmate. Inflorescences basically thyrsoid, very variable, often with well-defined main axis and/or distinct cymes, rarely a sessile axillary fascicle. Ovules 1 per locule of ovary. Seed sometimes carunculate, sometimes arillate.

About 322 genera and 8910 species: widespread throughout the world, primarily in the tropics and subtropics, more poorly represented in temperate regions; 75 genera (one endemic, nine introduced) and 406 species (99 endemic, 27 introduced) in China, nearly 95% of which are found in the S and SW parts of the country.

Fifty-nine genera and over 1700 species: mostly tropical, the greatest diversity in SE Asia; 16 genera and 138 species (41 endemic, four introduced) in China.

Four genera and ca. 210 species: throughout the tropics; two genera and 13 species (three endemic) in China.

Two hundred and eighteen genera and over 5700 species: widespread throughout the world, primarily in the tropics and subtropics, more poorly represented in temperate regions; 54 genera (one endemic, nine introduced) and 255 species (55 endemic, 23 introduced) in China.

The Euphorbiaceae as treated here include the following families that have been proposed for segregation: Androstachydaceae, Antidesmataceae, Bischofiaceae, Hymenocardiaceae, Phyllanthaceae, Pedilanthaceae, Picrodendraceae, Porantheraceae, Putranjivaceae, Ricinocarpaceae, Scepaceae, Stilaginaceae, Trewiaceae, and Uapacaceae. The Pandaceae and Buxaceae, formerly included here, are now well established as separate families.

Molecular data has shown that the traditional concept of Euphorbiaceae includes three major lineages that are relatively distantly related to each other: the Phyllanthoids (genera 1-16 in this account), the Putranjivoids (genera 17 and 18), and the Euphorbioids (genera 19-75).

Many species of Euphorbiaceae are of economic importance, probably most importantly as the main source of rubber (Hevea) but also as sources of medicine; foods, both as a staple starch source (Manihot) and fruits (e.g., Phyllanthus emblica); seed oils (Ricinus, Vernicia); and insecticides.

Li Pingt’ao. 1994. Euphorbiaceae. In: Li Pingt’ao, ed., Fl. Reipubl. Popularis Sin. 44(1): ii-viii, 1-217; Kiu Huashing, Hwang Shumei & Chang Yongtian. 1996. Euphorbiaceae (2). In: Kiu Huashing, ed., Fl. Reipubl. Popularis Sin. 44(2): ii-ix, 1-212; Ma Jinshuang & Tseng Yungchien. 1997. Euphorbiaceae (3). In: Ma Jinshuang, ed., Fl. Reipubl. Popularis Sin. 44(3): ii-vi, 1-150.

The Putranjivoid genera resemble phyllanthoids by their 2-ranked leaves, frequently rather small fasciculate flowers, and ovules 2 per locule. They can be distinguished by their leaf blades, stigmas, and fruit. Also, the leaves contain mustard oils and so frequently taste peppery when fresh, although the taste may take a little time to develop.


Key 3. Euphorbioid genera

1 Lianas or subshrubs, stems twining or scandent, stinging hairs often present   (2)
+ Trees, shrubs, or herbs, stems not twining, stinging hairs never present   (5)
       
2 (1) Inflorescences capitate, long pedunculate, subtended by 2 large involucral bracts; male flowers 3 to many per bract; stamens more than 10.   44 Dalechampia
+ Inflorescences racemelike; male flowers 1 per bract; stamens 2 or 3   (3)
       
3 (2) Male calyx lobes 4(-6); stamens 2(or 3), anthers subsessile; styles partly connate into a stout column, free tips recurved.   43 Pachystylidium
+ Male calyx lobes 3; stamens 3, anthers on short stout filaments; styles not as above   (4)
       
4 (3) Connectives of stamens with inflexed, linear appendages; styles mostly free, spreading, and plumose.   41 Cnesmone
+ Connectives of stamens without appendage; styles connate into a massive subglobose or clavate structure, 3-lobed at apex, not plumose.   42 Megistostigma
       
5 (1) Indumentum with stellate hairs, peltate scales, and/or T-shaped hairs, sometimes also with simple hairs and/or glandular hairs or scales   (6)
+ Indumentum with simple and/or glandular hairs   (21)
       
6 (5) Male petals present; inflorescence usually bisexual (unisexual in Deutzianthus), usually racemelike, sometimes a conical panicle   (7)
+ Male petals absent; inflorescences variable, bisexual or unisexual   (14)
       
7 (6) Filaments incurved in bud; leaves with glands at junction of petiole and leaf blade and also often on leaf margin.   45 Croton
+ Filaments erect in bud; leaves often without such glands   (8)
       
8 (7) Herbs, stems woody at base; leaves less than 10 cm; stamens 5-15   (9)
+ Trees; leaves large, (7-)10-20(-24) × (4-)7-17(-20) cm; stamens 15-70   (10)
       
9 (8) Inflorescences terminal; male flowers 1-4 per bract; filaments free.   20 Speranskia
+ Inflorescences axillary; male flowers 1 per bract; filaments connate.   21 Chrozophora
       
10 (8) Stamens 50-70; inflorescence spikelike with female flowers proximal to male; fruit dehiscent.   19 Sumbaviopsis
+ Stamens 7-20; inflorescence a conical panicle with female flowers distal to male, or inflorescences unisexual; fruit indehiscent   (11)
       
11 (10) Evergreen trees; young branches and leaves stellate-hairy; stamens 15-32; ovary 2(or 3)-locular; exocarp fleshy.   47 Aleurites
+ Deciduous trees; young branches and leaves glabrous or puberulent; stamens 7-12; ovary 3-locular; exocarp crustaceous   (12)
       
12 (11) Petiole with 2 apical disciform glands; plants dioecious; male calyx 5-fid.   50 Deutzianthus
+ Petiole without glands; plants monoecious; male calyx 2- or 3-lobed   (13)
       
13 (12) Inflorescences and fruits stellate-tomentose, bracts conspicuous; flowers smaller, densely flowered; petals uniformly crimson-red; anthers extrorse; pedicels of fruits very short.   48 Reutealis
+ Inflorescences and fruits glabrous or puberulent, hairs simple or T-shaped, bracts inconspicuous; flowers larger, sparsely flowered; petals white with red veins; anthers introrse; pedicels of fruits longer.   49 Vernicia
       
14 (6) Plants usually dioecious; stamens 15-250   (15)
+ Plants monoecious, rarely dioecious (Endospermum); stamens 3-15   (16)
       
15 (14) Leaves and inflorescences lacking glandular scales, only stellate or scale hairs present; leaves alternate; capsule smooth, often 2-lobed.   26 Melanolepis
+ Lower leaf surface and/or inflorescences with glandular scales (whitish to yellowish, orangish, or reddish dots), sometimes hidden by dense stellate hairs; leaves opposite or alternate; capsule smooth or softly spiny, mostly 3-lobed.   24 Mallotus
       
16 (14) Leaves palmately veined, petiole insertion sometimes narrowly peltate; shrubs to 2.5 m tall; female sepals 6-13 mm.   35 Cladogynos
+ Leaves pinnately veined, never peltate; large shrubs or trees 3-35 m tall; female sepals 2-5 mm   (17)
       
17 (16) Stems tomentose; trees or shrubs 3-15 m tall; leaf base without glands or stipels, broadly cuneate, obtuse, or cordate   (18)
+ Stems pubescent or densely puberulent, glabrescent; trees 10-25 m tall; leaf base with a pair of glands or minute stipels, cuneate or truncate   (19)
       
18 (17) Inflorescence terminal, branched; stamen filaments slender, free; calyx glabrous.   36 Epiprinus
+ Inflorescence axillary, unbranched; stamen filaments as wide as anthers, joined at base; calyx stellate hairy.   37 Koilodepas
       
19 (17) Petiole 0.3-0.5 cm; fruit a densely tuberculate-spiny capsule.   38 Cephalomappa
+ Petiole 1-9 cm; fruit an unarmed drupe   (20)
       
20 (19) Petiole 1-4 cm; drupe puberulent, 3-5 cm in diam.; plants usually monoecious.   39 Cleidiocarpon
+ Petiole 4-9 cm; drupe ca. 1 cm in diam.; plants usually dioecious.   62 Endospermum
       
21 (5) Latex white, usually copious   (22)
+ Latex absent or watery or colored, never white   (35)
       
22 (21) Leaves palmately 3-5-foliolate or deeply 3-9-lobed; plants usually cultivated   (23)
+ Leaves entire, rarely shallowly lobed; plants mostly wild   (24)
       
23 (22) Leaves palmately 3-5-foliolate, not peltate; inflorescences axillary, sometimes at leafless nodes.   46 Hevea
+ Leaves palmately 3-9-lobed, petiole insertion often peltate; inflorescences terminal or leaf-opposed.   59 Manihot
       
24 (22) Inflorescence a cyathium, resembling a single flower, true flowers very reduced: perianth extremely reduced, mostly absent, male flowers reduced to single stamen, female to bare ovary, these enclosed within a cupular involucre, usually with a single terminal female flower and 4 or 5 lateral groups of male flowers and with conspicuous cyathial glands near margin; styles mostly bifid   (25)
+ Inflorescences elongated, usually with female flowers at base and male flowers toward apex, never enclosed within involucre; male calyx usually present; styles often simple   (26)
       
25 (24) Cyathium radially symmetrical, glands inserted on outside of cyathium.   74 Euphorbia
+ Cyathium distinctly bilaterally symmetrical, glands hidden within a well-developed nectar spur.   75 Pedilanthus
       
26 (24) Perennial herbs; stems and leaves sparsely puberulent; fruit a capsule, each lobe with 2 lines of conical spines.   66 Microstachys
+ Trees or shrubs; stems and leaves glabrous; fruit a drupe or capsule, not spiny   (27)
       
27 (26) Fruit a many-loculed woody schizocarp, 8-9 cm in diam., eventually breaking into curved segments; female flower with dark purple stigma 1.5-2.5 cm wide; anthers connate; trunk and branches spiny.   73 Hura
+ Fruit a 2- or 3-loculed capsule or drupe, up to 1.5 cm in diam., female flower with stigma much smaller; anthers free, filaments connate; spines absent   (28)
       
28 (27) Male sepals distinct, oblong-lanceolate; inflorescences bisexual or unisexual, axillary or terminal, if all female then axillary and plants growing on or near sea coast; leaves opposite or alternate.   65 Excoecaria
+ Male calyx shallowly 2-5-lobed; inflorescences bisexual, always terminal or leaf-opposed; leaves always alternate   (29)
       
29 (28) Stipules large, concealing apical bud, deciduous; male calyx laterally compressed, free; leaves with petiolar glands.   64 Homalanthus
+ Stipules small or absent; male calyx not laterally compressed; leaves with or without petiolar glands   (30)
       
30 (29) Leaf blade margin conspicuously serrate or undulate   (31)
+ Leaf blade margin entire or serrulate   (32)
       
31 (30) Petiole apex with 2 distinct adaxial glands; axis of inflorescence glabrous; exocarp slightly fleshy.   67 Falconeria
+ Petiole apex without glands; axis of inflorescence pilose; exocarp thick and hard.   70 Shirakiopsis
       
32 (30) Petiole not winged and without glands   (33)
+ Petiole winged and/or with apical glands   (34)
       
33 (32) Inflorescence 4-12 cm; fruit an indehiscent berry.   68 Balakata
+ Inflorescence ca. 2 cm; fruit a capsule.   71 Gymnanthes
       
34 (32) Petiole winged; seeds without aril; leaf blade with lowermost pair of veins originating distinctly above base, not forming basal margin.   72 Neoshirakia
+ Petiole not winged; seeds enclosed by thin waxy aril; leaf blade with lowermost pair of veins originating at very base, forming basal margin.   69 Triadica
       
35 (21) Leaf blade with dense hyaline spots; inflorescence a small leaf-opposed cyme.   60 Suregada
+ Leaf blade without hyaline spots; inflorescence axillary or terminal   (36)
       
36 (35) Leaves abaxially and often ovary and fruit with glandular scales or gland-tipped hairs   (37)
+ Leaves apparently without glandular scales and gland-tipped hairs   (39)
       
37 (36) Leaves opposite but with one member of each pair much smaller and stipulelike; styles 10-25 mm; indumentum with gland-tipped hairs.   22 Hancea
+ Leaves alternate or if opposite then similar in form; styles 1.5-7(-10) mm; indumentum with sessile glandular scales, often brightly colored   (38)
       
38 (37) Inflorescences terminal or leaf-opposed, rarely axillary; anthers 2-locular; styles stout.   24 Mallotus
+ Inflorescences axillary; anthers 3- or 4-locular; styles short or long and slender.   25 Macaranga
       
39 (36) Leaves opposite   (40)
+ Leaves alternate, sometimes congested into whorls   (43)
       
40 (39) Paired leaves equal; indumentum without glandular hairs, hairs not tufted   (41)
+ Paired leaves unequal; indumentum with glandular hairs and/or tufted hairs   (42)
       
41 (40) Herbs, 0.3-1 m tall; fruit a 2-lobed capsule, lobes abaxially 2-4-muricate or verruculose.   31 Mercurialis
+ Trees or shrubs, 3-11 m tall; fruit a globose capsule, not ornamented.   58 Erismanthus
       
42 (40) Fruit indehiscent; styles 20-25 mm; anther connective narrow.   23 Trevia
+ Fruit dehiscent; styles 1.5-7(-10) mm; anther connective often broad and conspicuous.   24 Mallotus
       
43 (39) Stamens very many, filaments connate for most of their lengths into several phalanges; if plant dioecious (Homonoia), then female flowers in axillary spikes and plant growing in riverbeds   (44)
+ Filaments free or connate only at base or plant dioecious and plant female   (46)
       
44 (43) Plants glabrous; leaves palmately lobed; inflorescences terminal, bisexual; male and female flowers clustered in bract-axils.   34 Ricinus
+ Young branches pubescent; leaves entire; inflorescences axillary, unisexual; male flowers solitary in bract-axils, female flowers solitary or in spikes   (45)
       
45 (44) Plants monoecious; female flowers solitary; fruits tuberculate; leaf blade oblong-oblanceolate or elliptic, 5-17 × 2-5 cm; trees or shrubs growing on forested slopes, often over limestone.   32 Lasiococca
+ Plants dioecious; female flowers in spikes; fruits pubescent, not tuberculate; leaf blade linear-oblong or narrowly lanceolate, 6-20 × 1.2-2.5 cm; shrubs growing in riverbeds.   33 Homonoia
       
46 (43) Leaves with 2 or more glands near junction between petiole and leaf blade   (47)
+ Leaves without glands at junction between petiole and leaf blade   (53)
       
47 (46) Leaf blade with stipels at base, palmately veined   (48)
+ Leaf blade without stipels at base, palmately or pinnately veined   (49)
       
48 (47) Stamens 25-60, thecae free; female calyx lobes valvate; styles bifid.   27 Discocleidion
+ Stamens usually 8, thecae connate; female sepals imbricate; styles undivided.   28 Alchornea
       
49 (47) Leaf blade palmately veined; male flowers with petals; plants mostly monoecious (Ostodes paniculata dioecious)   (50)
+ Leaf blade pinnately veined; male flowers without petals; plants dioecious   (51)
       
50 (49) Inflorescence a pedunculate cyme, bisexual; stamens 8-12, inner ones with fused filaments.   52 Jatropha
+ Inflorescence a thyrse, branched or unbranched, sometimes unisexual (plant dioecious); stamens 20-40, free.   55 Ostodes
       
51 (49) Stamens 4-8, filaments joined at base; male disk absent; styles undivided, filiform.   28 Alchornea
+ Stamens 10-20, or more, filaments free; male disk present; styles bifid or plumose   (52)
       
52 (51) Male sepals (2 or)3 or 4, imbricate; male disk annular; styles papillose or plumose; seeds globose or subglobose.   30 Claoxylon
+ Male sepals (4 or)5 or 6, valvate; male disk with many short, erect glands; styles bifid; seeds ellipsoidal or ovoid.   61 Baliospermum
       
53 (46) Inflorescence a unisexual axillary sessile fascicle; fruit densely spinescent; stamen (5-)8-15, filaments connate.   63 Chaetocarpus
+ Inflorescence elongated with distinct main axis; fruit smooth, tuberculate, or sparsely spiny; stamens mostly free (filaments connate in Dimorphocalyx)   (54)
       
54 (53) Inflorescences with terminal female flower with prominent clavate pedicels; stamens 3(-5).   57 Trigonostemon
+ Inflorescences unisexual or with proximal female flowers and distal male flowers; stamens (7 or)8 or more   (55)
       
55 (54) Stamens (7 or)8; anther locules long and slender, flexuous-contorted; female flowers often hidden within large bracts; styles laciniate.   40 Acalypha
+ Stamens 10-200; anther locules ellipsoid to oblong, straight; styles bifid   (56)
       
56 (55) Stamens 25-80(-100); male flowers without petals; plants monoecious.   29 Cleidion
+ Stamens 10-30; male flowers with petals; plants monoecious or dioecious   (57)
       
57 (56) Female petals present; stamen filaments connate or free   (58)
+ Female petals absent; stamen filaments free   (59)
       
58 (57) Filaments connate; inflorescence ca. 1 cm, few flowered.   56 Dimorphocalyx
+ Filaments free; inflorescence 8-30 cm, many flowered.   51 Codiaeum
       
59 (57) Female sepals with very conspicuously glandular-fimbriate margins; seed with caruncle.   54 Strophioblachia
+ Female sepals without fimbriate margins; seed without caruncle.   53 Blachia

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