The commissioner of agriculture, in person or by some person authorized by him, shall have free access to any place or conveyance wherein farm products are being marketed, transported or held for commercial purposes. The commissioner of agriculture, in person or by some person authorized by him, shall have power to open any bag, crate or other container of such farm products and examine the contents thereof, and may, upon tendering the market price, take samples therefrom. The commissioner of agriculture may employ inspectors to inspect farm products in accordance with established official grades or standards for the purpose of determining and certifying the quality and condition thereof and other material facts relative thereto. Certificates issued in pursuance of such inspection and executed by the inspector shall state the date and place of inspection, the grade, condition and approximate quality of the farm products inspected and any other pertinent facts that the commissioner may require. Such a certificate and all federal certificates relative to the condition or quality of such farm products shall be prima facie evidence in all courts of the state of the facts required to be stated therein: Provided, however, That the provisions of this act shall not apply to the grower in the sale of farm products grown by himself when made direct to the consumer.