The author describes some structural aspects of the leaflets of Spathodea nilotica Seem., an african bignoniacea cultivated in the State of São Paulo, for arborization of streets. The structure of the leaflets is studied from the point of view of its abnormal behaviour when in conditions of great loss of water by transpiration. The leaflets are hypostomatic. The adaxial epidermis is glabrous and the abaxial one has big tricelular hairs in the regions of the veins. The stomata are protruse, located in the interfibrovascular regions of the epidermis. The mesophyll is heterobaric and has three layers of palisade parenchyma. The spongy parenchyma is compound of ellipsoidal cells in parallel moniliform rows, running from the palisade parenchyma to the abaxial epidermis. The cuticles is very thin and shows subcuticular spaces. The author suggests that the presence of the subcuticular spaces allied to the heterobaric structure of the mesophyll may have influence in a possible partial detachment of the cuticle, when in conditions of great loss of water, which may provoke a sudden rolling up of the leaflet.