Several types of fruit occur in Euphorbiaceae, notably the explosively dehiscent dry fruit, and different seed-coat anatomies with taxonomic importance. This paper aims to describe the pericarp ontogeny and structure in Euphorbia milii Desmoul., and evaluate the presence of the secretory exotesta and caruncle. The fruit is a schizocarp, whose the pericarp development begins with a periclinal division of the inner epidermal cells. The derived cells divide, forming about four layers of obliquely elongated cells. Then, the adjacent parenchyma cells elongate, giving rise to a palisade layer and finally, the cells between this layer and the vascular strands undergo mitosis, originating about four layers of elongated cells perpendicularly to the inner oblique cells. These three zones lignify, while the region between the vascular strands and the exocarp, where idioblasts, hypodermis and laticifers are present do not show significant changes. Before the dehiscence, a lysis of cells of the septa and the desiccation of the fruit occur, which causes contraction of the non-lignified tissues and tension between the lignified zones, promoting rupture of each mericarp from central columella and on the dorsal strand, ejecting the seeds. The seeds have pseudocaruncle and the exotesta secretes mucilage, facilitating their imbibition.623477489Berg, R.Y., Myrmecochorous plants in Australia and their dispersal by ants (1975) Australian Journal of Botany, 23, pp. 475-508Boesewinkel, F.D., Bouman, F., The seed: Structure (1984) Embryology of Angiosperms, pp. 567-610. , Johri, B.M., Springer, BerlinBor, J., Bouman, F., Development of ovule and integuments in Euphorbia milii and Codiaeum variegatum (1974) Phytomorphology, 24, pp. 280-296Cain, A.J., The use of Nile Blue in the examination of lipids (1947) Quarterly Journal of Microscopical Science, 88, pp. 383-392Carlquist, S., The biota of long-distance dispersal. III. Loss of dispersibility in the Hawaiian Flora (1966) Brittonia, 18, pp. 310-335Esser, H., Fruit characters in Malesian Euphorbiaceae (2003) Telopea, 10, pp. 169-177Fahn, A., (1990) Plant Anatomy. 4ed., p. 588. , Pergamon Press, OxfordGabe, M., (1968) Techniques Histologiques, p. 1113. , Masson & Cie, ParisGanter, P., Jollés, G., (1969) Histologie Normale et Pathologique, 2, p. 1904. , Gauthier-Villars, ParisGerlach, D., (1984) Botanische Mikrotechnik: Eine Einführung. 3ed., p. 311. , Georg Thieme, StuttgartGerrits, P.O., (1991) The Application of Glycol Methacrylate in HistotechnologySome Fundamental Principles, p. 80. , Department of Anatomy and Embryology, State University Groningen, GroningenGregory, M., Baas, P., A survey of mucilage cells in vegetative organs of the dicotyledons (1989) Israel Journal of Botany, 38, pp. 125-174High, O.B., (1984) Lipid Histochemistry, p. 68. , Oxford University Press, New YorkHyde, B.B., Mucilage-producing cells in the seed coat of Plantago ovata: Developmental fine structure (1970) American Journal of Botany, 57, pp. 1197-1206Jimenez, M.S., Morales, D., Histología floral y desarrollo del fruto de Euphorbia atropurpurea Brouss (1978) Vieraea, 8, pp. 131-143Johansen, D.A., (1940) Plant Microtechnique, p. 523. , McGraw-Hill, New YorkJordan, M.S., Hayden, W.J., A survey of mucilaginous testa in Chamaesyce (1992) Collectanea Botanica, 21, pp. 79-89Jordan, L.S., Jordan, J.L., Jordan, C.M., Changes induced by water on Euphorbia supina seed coat structures (1985) American Journal of Botany, 72, pp. 1530-1536Kapil, R.N., Bor, J., Bouman, F., Seed appendages in angiosperms. I. Introduction (1980) Botanische Jahrbücher für Systematik, 101, pp. 555-573Lavialle, P., Delacroix, J., La paroi du pistil et du fruit dans le genre Euphorbia (1922) Comptes Rendus Hebdomadaires des Séances de L'Académie des Sciences, 175, pp. 179-181Lavialle, P., Delacroix, J., Caractères de l'endocarpe dans le genre Euphorbia (1922) Bulletin de la Société Botanique de France, 69, pp. 523-527Lavialle, P., Delacroix, J., Caractères histologiques du péricarpe et déhiscence du fruit chez les Euphorbes (1922) Bulletin de la Société Botanique de France, 69, pp. 585-590Lillie, R.D., (1965) Histopathologic Technic and Practical Histochemistry. 3ed., p. 715. , McGraw-Hill, New YorkLisci, M., Bianchini, M., Pacini, E., Structure and function of the elaiosome in some angiosperm species (1996) Flora, 191 (2), pp. 131-141Lisci, M., Pacini, E., Fruit and seed structural characteristics and seed dispersal in Mercurialis annua L. (Euphorbiaceae) (1997) Acta Societatis Botanicorum Poloniae, 66, pp. 379-386Liszt, K., Sárkány, S., Kadej, J., Kovács, A., Light and electron microscopic observations in connection with the developing pistil and seedappendix (caruncle) of Ricinus communis L (1981) Acta Societatis Botanicorum Poloniae, 50, pp. 345-348McManus, J.F.A., Histological and histochemical uses of periodic acid (1948) Stain Technology, 23, pp. 99-108Muzik, T.J., Development of fruit, seed, embryo, and seedling of Hevea brasiliensis (1954) American Journal of Botany, 41, pp. 39-43Narbona, E., Arista, M., Ortiz, P.L., Explosive seed dispersal in two perennial Mediterranean Euphorbia species (Euphorbiaceae) (2005) American Journal of Botany, 92 (3), pp. 510-516O'brien, T.P., Feder, N., McCully, M.E., Polychromatic staining of plant cell walls by toluidine blue O (1964) Protoplasma, 59, pp. 368-373Oliveira, J.H.G., Oliveira, D.M.T., Morfoanatomia e ontogênese do pericarpo de Manihot caerulescens Pohl e M. tripartita Müll.Arg. (Euphorbiaceae) (2009) Revista Brasileira de Botânica, 32, pp. 117-129Pearse, A.G.E., (1985) Histochemistry: Theoretical and Applied. 4ed., 2, p. 624. , C. Livingstone, EdinburghPizzolato, T.D., Staining of Tilia mucilages with Mayer's tannic acid- ferric chloride (1977) Bulletin of the Torrey Botanical Club, 104, pp. 277-279Du Sablon, L., Recherches sur la déhiscence des fruits a péricarpe sec. Annales des Sciences Naturelles (1884) Botanique et Biologie Vegetale, 18, pp. 5-104Simon, J., Molero, J., Blanché, C., Fruit and seed morphology of Euphorbia aggr. flavicoma. Taxonomic implications (1992) Collectanea Botanica, 21, pp. 211-242Singh, R.P., Structure and development of seeds in Euphorbia helioscopia (1969) Botanical Magazine Tokyo, 82, pp. 287-293Subils, R., Las especies de Euphorbia de la Republica Argentina (1977) Kurtziana, 10, pp. 83-248Tokuoka, T., Tobe, H., Ovules and seeds in Euphorbioideae (Euphorbiaceae): Structure and systematic implications (2002) Journal of Plant Research, 115, pp. 361-374Toledo, A.P., Anatomia e desenvolvimento ontogenético do fruto e da semente de mandioca (1963) Bragantia, 22, pp. 71-76Webster, G.L., Classification of the Euphorbiaceae (1994) Annals of the Missouri Botanical Garden, 81, pp. 3-32Werker, E., (1997) Seed Anatomy (Handbuch der PflanzenanatomieBd. 10, Teil 3), p. 424. , Gebrüder Borntraeger, Berlin