The various county treasurers shall not issue any tax-sale certificates nor shall the various county clerks execute any tax deeds prior to September 1, 1941, for lands bid off for taxes in the name of the county: Provided, That if such lands have not been redeemed prior to September 1, 1941, tax-sale certificates and tax deeds shall be issued and executed as provided by law: Provided further, That tax deeds may be executed in those instances where tax-sale certificates have been assigned prior to the effective date of this act [*].