The park police pension fund in each county shall be managed and controlled by the park commission of that county. The secretary of the commission shall be treasurer, ex officio, of the fund, and all moneys of the fund shall be received and disbursed by him, and shall be deposited in such bank or banks of deposit as the commission shall designate. The treasurer shall give bond in such sum as the commission shall determine, with sufficient sureties to be approved by it, for the faithful performance of his duties. If the surety is a corporation, the premiums shall be paid by the commission from the funds under its control. The commission shall invest and keep invested the moneys of the fund, so far as the same can be done, in securities authorized by law for the investment of trust funds.