The books and supplies so purchased shall be under the charge of the board, who may select one or more persons within the county to keep said books and supplies as the depository agent of the board under such rules and regulations as the board shall adopt. The board shall require of each person so appointed a bond in such sum as may seem to the board to be desirable, the reasonable cost of which, if a bond of an association or corporation as surety is furnished, shall be paid by the district. The board shall adopt rules and regulations to provide that no textbook in any branch determined by the board to be taught in the schools under its charge, shall be sold or rented by such depository agent to the pupils in such schools as a textbook other than those textbooks authorized by said board for use by the pupils in such schools; to provide that no such textbook shall be sold or rented by such depository agent at a price or fee higher than that fixed by the said board; and to provide such other measures not in conflict with law as are necessary properly to govern said depository agents and safeguard the said books and moneys.