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FOC | Family List | FOC Vol. 11 | Euphorbiaceae

45. Croton Linnaeus, Sp. Pl. 2: 1004. 1753.

巴豆属 ba dou shu

Authors: Bingtao Li & Hans-Joachim (Hajo) Esser

Tridesmis Loureiro.

Trees or shrubs, rarely subshrubs, monoecious or more rarely dioecious; latex clear or reddish, often scanty or apparently absent; indumentum of stellate hairs and/or peltate scales. Leaves alternate, rarely opposite or nearly verticillate; stipules present or absent; petiole with or without apical paired glands; leaf blade simple, margin entire or denticulate, often with glands; venation pinnate or palmate. Inflorescences terminal or axillary, racemelike thyrses, often with proximal solitary female flowers and distal male flowers, often in clusters. Male flowers: sepals mostly 5, imbricate to valvate, free; petals 5, smaller or nearly equal to sepals; disk glandular, usually 5, and opposite sepals; stamens 10-20; filaments free, inflexed in bud; anthers muticous; pistillode absent. Female flowers: sepals 5, often narrower than in male, imbricate to reduplicate-valvate, persistent, sometimes accrescent; petals 5, smaller than in male, mostly reduced or obsolete; disk annular or dissected, receptacle often villous; ovary 3-locular; ovules 1 per locule; styles 3, longer and slender, free or nearly so, once to several times bifid. Fruit a capsule dehiscing into 3 2-valved cocci, more rarely ± indehiscent and fleshy, drupelike or berrylike. Seeds usually smooth, carunculate; testa crustaceous; endosperm copious, fleshy; cotyledon broad and flattened.

Nearly 1300 species: tropics and subtropics of the world, most numerous in the neotropics; 23 species (15 endemic) in China.

Many species are used medicinally. Several are extremely toxic. Croton moonii Thwaites (瘤果巴豆 liu guo ba dou), native to Sri Lanka, is cultivated for medicine in S Guangdong.

1 Young branches, inflorescences, and fruits with appressed membranous peltate scales   (2)
+ Young branches stellate-hairy, stellate-scaled, or subglabrous   (5)
2 (1) Leaf blade leathery; capsule ovoid-ellipsoid or oblong, 2.5-3.5 cm.   1 C. joufra
+ Leaf blade papery or thinly papery; capsule subglobose, 0.4-1 cm   (3)
3 (2) Leaf margins serrate, both surfaces olivaceous when dry, abaxially sparsely scaly.   2 C. mangelong
+ Leaf margins entire, glaucous-gray to gray-brown when dry, abaxially densely scaly   (4)
4 (3) Leaf blade 3-veined from base, adaxially sparsely hairy; styles bifid.   3 C. kongensis
+ Leaf blade pinnately veined, adaxially glabrous; styles 4-8-fid.   4 C. cascarilloides
5 (1) Leaf blade palmately 3-5(-7)-veined   (6)
+ Leaf blade pinnately veined   (15)
6 (5) Leaf blade palmately (3-)5(-7)-veined   (7)
+ Leaf blade palmately 3(-5)-veined   (9)
7 (6) Leaf blade papery, abaxially glabrescent, glands at apex of petioles stalked.   5 C. euryphyllus
+ Leaf blade thinly leathery, abaxially persistently densely stellate-hairy, glands sessile or stalked   (8)
8 (7) Leaf blade rotund to broadly ovate, glabrescent adaxially, basal glands sessile; fruits sparsely stellate-pubescent.   6 C. yunnanensis
+ Leaf blade ovate, rarely ovate-elliptic, sparsely stellate-pubescent adaxially, glands at apex of petioles stalked; fruits with densely waxy-yellow scurfy hairs.   7 C. yanhuii
9 (6) Bract margins with linear-lanceolate teeth, apex of teeth with capitulate glands; styles 4-lobed.   8 C. crassifolius
+ Bract margins entire; styles 2-lobed   (10)
10 (9) Glands of leaf base or petiole apex cupular, stalked   (11)
+ Glands of leaf base or petiole apex discoid, sessile   (13)
11 (10) Young branches, leaves, and inflorescences with purple-brown or purplish waxy stellate pubescence, older leaves glabrous.   9 C. purpurascens
+ Young branches, leaves, and inflorescences with yellow-gray stellate hairs, older leaves persistently so   (12)
12 (11) Leaf margins denticulate, leaf blade petiolar glands short and broad.   10 C. lachnocarpus
+ Leaf margins double-serrate, leaf blade basal glands longer and slender.   11 C. cnidophyllus
13 (10) Shrubs scandent; young branches and older leaves hispid; petiole to 1.5 cm, apex with glands; fruits globose.   12 C. caudatus
+ Shrubs or treelets; young branches sparsely stellate-hairy, older leaves glabrous; petiole 2.5-10(-14) cm; fruits ellipsoidal   (14)
14 (13) Leaves papery, 2-7 cm wide, glands on base; male sepals glabrous at apex.   13 C. tiglium
+ Leaves thinly leathery, 7-14 cm wide; glands on petiole apex; male sepals woolly.   14 C. damayeshu
15 (5) Ovary and fruits glabrous; leaf blade papery, basal glands sessile and cupular.   15 C. chunianus
+ Ovary and fruits with stellate hairs or stellate scale-hairs; leaf blade basal glands sessile or cupular   (16)
16 (15) Leaf blade base or petiole apex with sessile, flat, or cupular glands   (17)
+ Leaf blade base or petiole apex with stalked and cupular glands   (20)
17 (16) Inflorescences glabrous; female petals filamentous or absent   (18)
+ Inflorescences hairy; female petals present, oblong   (19)
18 (17) Leaves thinly leathery, abaxially with scurfy stellate hairs; petioles with cupular glands at apex.   20 C. laniflorus
+ Leaves papery, glabrous on both surfaces, base with flat glands.   21 C. dinghuensis
19 (17) Young branches and inflorescences with densely scurfy stellate scale-hairs; leaves glaucous-gray, base with semiorbicular glands.   22 C. laevigatus
+ Young branches and inflorescences densely stellate-pubescent; leaves yellow-brown when dry, base with cupular glands.   23 C. laui
20 (16) Leaf blade not olivaceous-green when dry, abaxially glabrous or tomentose   (21)
+ Leaf blade olivaceous-green when dry, abaxially glabrous   (22)
21 (20) Young branches and inflorescences with stellate scale-hairs; leaves papery, oblong-lanceolate, glabrous on both surfaces; petiole short, less than 1 cm.   18 C. hancei
+ Young branches and inflorescences stellate-tomentose; leaves thickly papery, long elliptic to oblong-elliptic, tomentose abaxially; petiole 1-6 cm.   19 C. merrillianus
22 (20) Young branches sparsely stellate-hairy; leaves smaller, 3-7 cm, margin entire, base with glands; petiole less than 1 cm.   16 C. howii
+ Young branches with appressed stellate hairs; leaves 7-14 cm, margin denticulate; petiole more than 1 cm, with glands at apex   (23)
23 (22) Leaf blade base cuneate, equilateral.   17 C. lauioides
+ Leaf blade base rounded or unequally cordate. ..... C. moonii (see note above)    

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