ABSTRACT Anatomy of rachis, petiole and petiolule in 43 species and 20 genera of Euphorbiaceae are investigated. The mechanical tissues in these organs are invariably sclerenchymatous and collenchymatous. The xylem elements are additionally mechanical in function. The occurrence of vascular tissues is in the form of distinct bundles, only an arc-shaped strand or a continuous cylinder. The cortical bundles are noted in Aporosa and Jatropha gossypiifolia while unequal sized central vascular bundles are observed in Mallotus nudiflorus and M. philippensis. The variation in the distribution of sclerenchyma, collenchyma and vascular patterns apart from the shapes as observed in a transverse section of the leaf stalk can be used for the delineation of the taxa studied. Key words: Anatomy, Leaf stalk, Mechanical tissues, Systematics, Euphorbiaceae. REFERENCES Aguiar, M.O. and Preisinger, H. 2000. Traits of leaf anatomy of Croton lanjouwensis Jablonski (Euphorbiaceae) in different strata of the plant. German - Brazilian Workshop on Neotropical Ecosystems - Achievements and Prospects of Cooperative Research Hamburg, pp. 961-964. Al-Nowaihi, A.S., Khalifa, S.F. and Ishak, I.F. 1980. The significance of comparative anatomy of the petiole in the identification of some Malvaceous taxa. Bull. Fac. Sci. Riyad Univ. 2: 25-41. Bhadane, V.V. 2006. Taxonomic significance of the structure of the rachis, petiole and petiolule in Meliaceae. Bioinfolet 3(4): 234-239. Datta, P.C. and Dasgupta, A. 1979. Comparison of vegetative anatomy of Piperales. III. Vascular supplies to leaves. Acta Bot. Indica 7: 39-46. De Candolle, C. 1879. Anatomie compare des feuilles de quelques families de dicotyledones, Mem. Soc. Phys. Hist. Nat. Geneve 26: 427-480. *Dehay, C. 1935. L’appareil libero-ligneaue foliare des Euphorbiacees. Ann. Sci. Natur. Bot. 10: 147-290. Dehgan, B. and Webster, G.L. 1979. Morphology and intrageneric relationships of the genus Jatropha (Euphorbiaceae). Univ. Cal. Publ. Bot. 74: 1-73. Dehgan, B. 1982. Comparative anatomy of the petiole and intrageneric relationship in Jatropha (Euphorbiaceae). Amer. J. Bot. 69 (8): 1283-1295. Dickison, W.C. 1969. Comparative morphology studies in Dilleniaceae - IV. Anatomy of node and vascularization of leaf. J. Arnold Arbor Havr. Univ. 50: 384-410. Ennos, A.I., H.Ch. Spatz and Speck, T.T. 2000. The function morphology of the petiole of the banana, Musa textilis. J. Expt. Bot. 51 (353): 2085-2093. Hare, C.L. 1944. On the taxonomic value of the an-atomical structure of vegetative organs of dicotyle-dons. V. The anatomy of petiole and its taxonomic value. Proc. Linn. Soc. Lond. 155: 223-229. Howard, R.A. 1962. The vascular structure of the petiole as taxonomic characters. Adv. Hort. Sci. 3: 7 - 13. Howard, R.A. 1970. Some observations on the nodes of woody plants with special reference to the problem of the “split-lateral” versus the “common gap”. In Robson, N.K.B., Cutler, D.F., Gregory, M. (eds.), New Research in Plant Anatomy. Bot. J. Linn. Soc. Suppl. 1, 63: 195-214. Lignier, M.O. 1887. Recherches sur I’ anatomie compare des calycanthees des Melastomacees et des Myrtaceae, Arch. Sci. Nord. De la France 4: 455. Khatijah, H., Bkhtiar, A.W. and Che P.T. 1996. Comparative leaf anatomical studies of some Mallotus Lour. (Euphorbiaceae) species. Bot. J. Linn. Soc. 112 (2): 137-153. Metcalfe, C.R. and Chalk, L. 1950. Anatomy of the Dicotyledons II. Clarendon Press, Oxford. Miller, K.I. and Webster, G.L. 1962. Systematic position of Cnidoscolus and Jatropha. Brittonia 14: 174-180. Murillo, J. 2002. Leaf anatomy of the subtribe Conceveibinae (Euphorbiaceae). Rev. Biol. Trop. 50(1): 9-20. Petit, L. 1886. Sur l’importance taxonomique du petiole, C.R. Acad. Sci. Paris 103: 767-769. Petit, L. 1887. Le petiole des dicotyledones au point de vue de l’anatomie comparee et de lataxinomie, Mem. Soc. Sci. Phys. Nat. Bordeaux. Mem. 3 (3): 217-404. Radcliffe-Smith, A. 2001. Genera Euphorbiacearum. Royal Botanical Gardens. Kew. 464p. Schofield, E.K. 1968. Petiole anatomy of Guttiferae and related families. Mem. N.Y. Bot. Gard. 18: 1-55. Solereder, H. 1908. Systematic Anatomy of the Dicotyledons Vol. 1, Clarendon Press, Oxford. Shaheen, A.M. 2006. The value of vascular supply of the petiole trace characteristics in the systematic of some species of subfamily: Mimosoideae- Leguminosae. Turkish J. Bot. 31 (4): 297-310. Stuessy, F.T. 1990. Plant taxonomy. The systematic evolution of comparative data. Columbia University Press, New York. Thakur, H.A. and Patil, D.A. 2011. Petiolar anatomy in some unstudied Euphorbiaceae. J. Phytol. 2(12): 54-59. Vesque, J. 1885. Caracteres des principales families gamopetales, Tires de l’anatomie de la feuille. Annals Sci. Nat. Bot., Ser. 7(1): 183-360. Webster, G.L. 1994. Synopsis of the genera and suprageneric taxa of Euphorbiaceae. Ann. Missouri Bot. Gard. 81: 33-144.