In addition to entries by freight or express provided for in § 319.41-5, importations are permitted by mail of mature corn on the cob from the countries specified in § 319.41-1(b)(2), and clean shelled corn and clean seed of the other plants covered by § 319.41, provided that a permit has been issued for the importation in accordance with §§ 319.7 through 319.7-5 and all conditions of the permit are met.