The board of county commissioners of any county may levy a tax, within the limitations prescribed by law, and appropriate money from the proceeds thereof or from the general fund of the county to be paid to the Ohio state university to the credit of the OSU extension fund created by section 3335.35 of the Revised Code and expended for the purposes prescribed in section 3335.36 of the Revised Code for the benefit of the citizens of that county. Any money paid into the fund under this section that aggregates more than ten per cent of the county appropriation in the preceding year and that remains unexpended for two years from the time of the payment shall be returned to the county from which it came unless the board of county commissioners determines by resolution to contribute it to OSU extension for general purposes.