The City Treasurer shall have custody of all money belonging to the Library Fund, including cash receipts, and shall pay out such money only upon proper vouchers; provided, however, the Library Board may keep a petty cash fund of not exceeding one hundred dollars ($100.00) for the handling of petty cash disbursements. The custodian of said petty cash fund shall be designated by the Library Board and shall be required to furnish a bond of not less than one thousand dollars ($1,000). Any money received by the Library in trust for specific purposes shall be paid out only in accordance with the terms of said trust. A report of all such gifts and disbursements made therefrom shall be included in the annual report to the City Council.  (1981 Code § 1.137)