Any surplus funds which said corporation may have in its treasury shall be invested by the board of directors in some perfectly secure real estate or securities, all of which shall be exempt from taxation, as is the property of other public corporations, and the board of directors shall exercise the best of care in the preservation of said properties and funds and the accumulation thereof, to the end that provisions may be made for the perpetual maintenance of said cemetery and the improvement, embellishing, beautifying and taking care thereof, for which purposes all of the funds of said corporation, after the payment of its debts, shall at all times be subject, to be applied.