A nurseryman or dealer may, under the certificate issued to him, ship nursery stock grown for him elsewhere or purchased by him from other states or countries, if such stock was received under a certificate, satisfactory to the department, that it had been inspected where grown and found to be apparently free from dangerously injurious insects and such as were liable to become so; and no such stock shall be sold within the state or shipped until the certificate accompanying it has been submitted to and approved by the department.
N.J.S. § 4:7-29