Contact with high dosages of carbaryl (1-naphthyl-N-methylcarbamate), Zectran (4-dimethylamino-3, 5-xylyl methylcarba-mate), Bayer 44646 (4-dimethylamino-m-tolyl methylcarbamate), EPTC (ethyl di-N-propyl thiolcarhamate), and 1-naphthol caused stunting of hypocotyl length and abnormalities of root-hair development in germinating seedlings of Nicotiana tabacum. All these compounds except Bayer 44646 caused marked inhibition of germination. Seedlings treated with carbaryl and 1-naphthol produced a characteristically zoned, blue coloration of the radicle which spread to other areas of the plant. Seedlings of N. sylvestris, N. glutinosa and Petunia hybrida treated with carbaryl produced radicles with blue coloration. Production of this coloration seemed to be dependent upon the presence of 1-naphthol or the 1-naphthyl group.