The Annonaceae juss. family comprises about 130 genera and 2500 species, of which 35 genera and 750 species are found in the Neotropics (Maas 1983). The purpose of this paper is to study the leaf anatomy of Annona squamosa L., aiming to support phytochemical studies. The samples were collected from the Research Campus of the Emílio Goeldi Museum of Pará (MPEG), Belém-PA. The material was fixed in FAA70%, using the usual techniques in plant anatomy. In frontal view, both epidermises show thin-walled heterodimensional wavy epidermal cells covered by an ornamented cuticle, but paracitic stomata and trichomes only on the abaxial surface. On the abaxial surface we found the presence of simple filiform non-glandular pluricellular trichomes and paracitic stomata. The dorsiventral mesophyll formed by palisade and lacunate parenchyma. The bi-stratified palisade parenchyma formed by uniform cells occupying approximately half of the mesophyll, followed by a lacunose parenchyma with irregular, heterodimensional cells, presenting intercellular spaces, secretory cavities, fibers, sclereids and crystals. We observed at the level of the central vein adaxial epidermis formed of square heterodimensional cells and those of the abaxial face are smaller also square and covered by a thickened cuticle and interrupted by 2 to 4 layers of lamellar type collenchyma, followed by a fundamental parenchyma, and in the central region collateral vascular bundles. Comparing the results of this study with those described by Metcalf & Chalk (1957), we verified certain anatomical characteristics common to the Annonaceae family, but A squamosa L. also presents characteristics specific to the taxon
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