Bonds issued pursuant to this chapter shall be issued for public improvements of the county and such other purposes as may from time to time be authorized by other provisions of general law, including without limitation, special improvements the cost of which is assessed or assessable in whole or in part against properties benefitted or improved by such improvements; provided that the issuance of those bonds for those special improvements shall be limited to special improvements initiated by the county. The purpose or purposes of issuance need not be stated in any bond.