Seeds contaminants are more likely from species with dehiscent fruits, though seeds from indehiscent fruits are also frequently found. Fact sheets include representative images or illustrations of seeds for every family, when available. Seeds of different taxa are differentiated by several characters, including: size and shape (sometimes variable within a species), color (not always reliable), location and nature of the hilum (i.e., the scar remaining where the seed had been joined to fruit tissues), shape of the embryo within the seed coat, surface texture, and the occurrence of wings or structures, such as arils or aril-like structures. Presence of arils or aril-like structures will quickly narrow down the possible families. However, they may be lost in transport, and the key and fact sheets takes this into account.