ABSTRACT We studied the leaf anatomy of 15 species of Byrsonima and a single species of Diacidia as an outgroup to test the relevance of leaf anatomical characters to the complicated taxonomy of this genus. We present complete anatomical descriptions for petioles and leaf blades, together with an anatomical matrix, dendrogram and an identification key for the studied taxa. The most informative characters were the presence of stomatal crest, trichome type, epidermis type, contour and conformation of the vascular system in the diaphragm and medium petiole and number of accessory bundles. The aforementioned characters revealed that the anatomy of the petioles in the genus differs from that of petioles in the outgroup taxon with regard to vascular system conformation and the absence of cortical sclereids. Furthermore, the anatomy of the leaf blade appears to be quite informative in Byrsonima, especially in synonymized species. The anatomical features evaluated here have great value for Byrsonima taxonomy. These features may be used in an evolutionary approach to the group, especially for proposing a new classification system based on morphoanatomical characters of the genus.

The vegetation of the Brazilian restinga (coastal woodland) presents a variety of species and different characteristics, encompassing fields, fruit groves and forests on quartzarenic neosols. We hypothesised that the structure of the restinga landscape along the coast of the state of Piauí is influenced by edaphic factors and presents a pattern similar to that of other northeastern restingas. We evaluated three restingas in Piauí, using the quarter method to determine their structure. Composite soil samples were collected to determine their chemical and physical properties. Edaphic variables were correlated with plant species by canonical correspondence analysis (CCA). Phytosociological data for all three areas indicated regenerating vegetation comprising several small individuals, 82.5% of which showed a diameter at ground level < 13 cm. We also observed considerable tillering. In two of the areas, there was a predominance of Fabaceae species, such as Caesalpinia pyramidalis and Copaifera martii. Although the structural characteristics of the restingas studied were similar to those of other northeastern restingas, the former showed lower Shannon diversity indices (2.18-2.44). The CCA indicated that species distribution was influenced by edaphic factors such as pH, aluminium content and amount of organic matter. The restingas studied were similar to others along the Brazilian coast.