The precise identification of the dispersal units of weed species, considered as prohibited or restrited noxious weed seeds by the Ministery of Agricuiture act number 443 of 11 november of 1986, constitutes a very important work during the purity tests and the exame of weed seeds. Seeds of Brassica campestris L. and Sinapis arvensis L. are very similar and several mistakes occur during the identification, so there are presented drawings, anatomo-morphological characterization of the seeds and morphological descriptions of the seedlings in order to help the discrimination between the two species. Studies on the morphology of the spikelets, cariopsis and seedlings of Pennisetum setosum (Sw.) L. Rich. were carried out together with the morphological characterization of the fertile glums, nutlet and seedlings of Cyperus sesquiflorus (Torr.) Mattf. et Kükenth. There are also indicated the common names, the crops in which the species occur as a weed and the agricultural seeds where the noxious seeds are found as impurities.