The developmental control of plant reproduction is often related to the activity of methylation-dependent pathways that play an essential role in genome integrity and the transgenerational establishment of epigenetic marks. Cytogenetic analysis and in situ patterns of protein expression are crucial to accurately establish the function and mode of action of genes involved in the epigenetic control of female meiosis and gametogenesis. Here, we describe a whole mount propidium iodine staining and immunolocalization procedures to study the role of proteins involved in RNA-directed DNA methylation during the development of ovules in Vigna unguiculata (cowpea). The procedure can be easily adapted to develop ovules of other legumes such as common bean and scarlet runner bean.