The identification of the dispersal units is of major importance among the procedures of a Seed Analysis Laboratory. The morphological characteristics of the dispersal units associated with the anatomical characteristics of the seeds, such as the shape, size and position of the embryo in relation of the storage tissue in order to help the separation of the weed species of Lantana camara L., Lantana lilacina Desf., Stachytarphetta polyura (Schauer.) DC. and Verbena bonariensis L.. There are presented drawings, morphological characteristics and two taxonomical keys in order to help the identification of the dispersal units and the seedlings. There are also indicated the common names, the crops m which the species occur as a weed and the agricultural seeds where the noxious seeds are found as impurities.