The president and secretary of the public library board shall certify monthly to the treasurer all amounts deducted in accordance with the provisions of this Division from the salaries paid by the public library board, which amounts, as well as all other sums contributed to said fund under the provisions of this Division, shall be set apart and held by said treasurer for the purpose hereinbefore specified, subject to the order of said board of trustees, and shall be paid out upon warrants signed by the president and secretary of said board of trustees.