Leaf morphological studies were made in two genotypes of peanut (Arachis hypogaea L.) of the Valencia group, complementing informations included in previous papers. Peanuts are an important worldwide cultivated crop which has it center of origin in Brazil. No research is known involving studies with the organography and anatomy of the Brazilian genotypes. The genotype SO-53 ('Tatu'), susceptible to all of the most important foliar diseases, occupies the major part of the cultivated peanut in Brazil. The genotype SO-909 (PI-259747) has been frequently mentioned as a source of resistant germplasm to the peanut foliar diseases in phytopathological papers. Macroscopic measurements, with the use of a pachymeter, as well as microscopic observations, by photo microscopy, were made. An organographic study was carried out with plants which were grown in field conditions, and the anatomical studies were made with the use of semi-permanent slides, through schematic drawings and photo microscopy. The idioblasts found in the leaflets were divided into three types, according to the presence of tannin, mucilage or cristal. The mucilage idioblasts could be separated into long and short types; the long appearing only on the adaxial leaflet surface, and the short, similar to epiderm cells, appearing on both surfaces. The hairs were divided into three types according to their size: long, short and very short. All types have one to four basal cells and a long apical cell. The bristles, with multicellular structure, were classified into two types: the large, visually observed, present mainly in the sheath, and the short, present along the leaflet borders. Some morphological characteristics such as hair presence and frequency, the shape of the adaxial division at the petiole rachis zone and the leaflet thickness can be used in the characteristics of peanut genotypes. To the 'Tatu', the minor thickness of leaflet and the presence of air spaces at epiderm to the abaxial surface, can be associated to the susceptibility to some foliar fungic diseases.
peanut; Arachis hypogaea L.; leaf; anatomy; organography