Botanical Survey of India | Flora of India

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Trees or shrubs, rarely herbs, monoecious or rarely dioecious, densely or sparsely clothed with stellate hairs or lepidote scales, occasionally glabrous; stems with coloured or rarely milky sap. Leaves simple, alternate, petiolate, penninerved or palmatinerved at base, with 2 (- 10) sessile or stipitate glands at junction of petiole and lamina; stipules caducous. Inflorescences terminal and sometimes axillary, racemiform cymes or thyrses, androgynous or occasionally unisexual; female flowers solitary at lower nodes; male flowers in fascicles at upper nodes; bracts shortly subulate or triangular. Male flowers: sepals (4 -) 5 (- 6), valvate; petals isomerous with free sepals; disc glands small, opposite to sepals; stamens 8 - 40, free, arranged in whorls; filaments mostly lanate towards base, inflexed at apex in bud; anthers basifixed, 2-loculed, the thecae usually parallel or slightly diverging, adnate to a broad connective, longitudinally dehiscent; pistillode absent; receptacle densely lanate or rarely glabrous. Female flowers: sepals (4 -) 5 (- 10), shortly connate at base, valvate or sub imbricate; petals 0 - 5 (-6), smaller than the sepals or vestigial; disc glands small; staminodes absent; ovary (2 -) 3 (- 5)-locular; styles 3, free or shortly connate below into a column, once or repeatedly bifid above into linear or thickened branches; ovule one per locule. Fruits capsular, smooth or often muriculate, usually 3-seeded; columella persistent; seeds usually 3-angled with a broad convex back, carunculate; testa dry, thin; endosperm copious; embryo straight; cotyledons broad.

Tropics and subtropics of Old and New World, the majority of the species being in South America and West Indies, ca 1200 species in the world. In Asia, ca 150 species occur in S. China, Indo-China, S. & SE. Asia and Malesia. In India 16 species are found.

Literature. CHAKRABARTY, T. & N. P. BALAKRISHNAN (1997). A revision of Croton L. (Euphorbiaceae) for Indian subcontinent. Bull. Bot. Surv. India 34: 1 - 88.

Notes. Species of Croton contain a great diversity of chemical compounds, viz. several kinds of alkaloids, saponins, tannins and flavanoids. Some species exhibit antimicrobial, antimalarial, antiatherogenic, androgenic, insecticidal and antitumour activities. There is great scope for further studies on the Phytochemistry of this genus.



KEY TO THE SPECIES


1 a. Introduced weedy herbs 2
b. Indigenous trees, shrubs (rarely scandent) or undershrubs 3
2 a. Plants sparsely whitish stellate-pubescent to glabrescent; trichomes soft, without erect central ray; leaves penninerved; glands at the base of lamina sessile; female sepals more or less e 3. Croton bonplandianus
b. Plants more or less densely ochraceous stellate-hirsute to scabrid; trichomes harsh with pronounced central ray; leaves strongly trinerved at base; glands at the base of lamina shortly stipitate; female sepals distinctly unequal 6. Croton glandulosus
3 a. Leaves densely or sparsely lepidote beneath 4
b. Leaves variously stellate-pubescent or glabrous beneath 7
4 a. Leaves strongly trinerved at base, more or less densely silvery, orange-brown, or golden lepidote above, stiff-coriaceous 13. Croton scabiosus
b. Leaves penninerved, distantly scattered lepidote or glabrous above, membrous to thin-coriaceous 5
5 a. Foliar glands stipitate; young leaves with fine detersible stellate hairs on upper surface; trichome- base mostly colourless; style-branches twice or thrice bifid; leaves often subopposite or pseudo-verticillate and separated by long internodes 16. Croton zeylanicus
b. Foliar glands sessile; young leaves with detersible lepidote scales on upper surface; trichomebase mostly coloured; style-branches once bifid; leaves never separated by long internodes 6
6 a. Fruits obovoid, large, 18 - 25 mm long, ca 15 mm across, shortly stipitate 11. Croton malabaricus
b. Fruits subglobose, smaller, 9 - 15 mm across, without a basal stipe 1. Croton argyratus
7 a. Indumentum of young shoots, petioles, rachis and flowers lepidote 8
b. Indumentum of young shoots, petioles, rachis and flowers stellate-pubescent or lacking 9
8 a. Leaves very coarsely dentate-serrate-crenate; webbing of scales at least 80%, free portion of rays radiating in one plane; ovary intruded at apex; fruits much smaller, subglobose, up to 1 cm long, 0.8 - 1.2 cm across, prominently lobed 12. Croton persimilis
b. Leaves shallowly or evenly serrate-dentate to subentire; webbing of scales 50% or less, free portion of rays radiating in all directions; ovary obtuse or rounded at apex; fruits ovoid- ellipsoid or oblong or obovoid, larger, 2.5 - 3.5 cm long, 2 - 2.5 cm across, obscurely lobed 7. Croton joufra
9 a. Leaves penninerved 10
b. Leaves strongly trinerved at base 13
10a. Ovary and fruits usually bilocular, rarely trilocular; basal glands of leaves thinly long-stipitate 10. Croton lissophyllus
b. Ovary and fruits always trilocular; basal glands of leaves subsessile or short stipitate 11
11a. Petioles narrowly and shallowly sulcate above; rachis tomentellous (Andaman Islands) 14. Croton sublyratus
b. Petioles distinctly deeply channelled above; rachis glabrous or almost so (Peninsular India) 12
12a. Fruits larger (10 - 14 mm in diam.); leaves usually larger (7 - 25 cm long); basal glands of leaves shortly stipitate; inflorescences usually elongate, 12 - 30 cm long 5. Croton gibsonianus
b. Fruits smaller (6 - 10 mm in diam.); leaves usually smaller (2 - 10 cm long); basal glands of leaves subsessile; inflorescences mostly shorter, 3 - 10 cm long 8. Croton klotzschianus
13a. Scandent shrubs or sometimes climbers 4. Croton caudatus
b. Erect shrubs, low undershrubs or trees 14
14a. Petioles 4 - 8 mm long; female sepals accrescent, 1.5 - 2 cm long; ovary glabrou 9. Croton lawianus
b. Petioles usually longer, 5 - 80 mm or more long; female sepals not accrescent, much shorter; ovary pubescent 15
15a. Leaves hispid, scabrid-pubescent, pilose or sparsely pubescent above; style- branches usually quadrifid; fruits 8 - 14 mm in diam., muricate, scattered pubescent 2. Croton aromaticus
b. Leaves glabrous above; style-branches usually bifid; fruits 13 - 25 mm in diam., smooth, subglabrous 15. Croton tiglium


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