The board of park commissioners of any city shall have power, subject to the limitations of this act, to issue general bonds of such city when they deem it necessary so to do, to pay for or obtain funds for the acquiring or improving of any park, parkway or boulevard of such city. Such bonds and interest thereon shall be paid by a general tax upon all the taxable property of the city or of any one or more park districts thereof, as shall be determined by the board at the time of the issuance thereof.