All sums of money received from the United States under an act of Congress, approved May 23, 1908, being an act providing for the payment to the states of twenty-five percent of all money received from the national forest reserves in the states to be expended as the legislature may prescribe for the benefit of the public schools and public roads of the county or counties in which the forest reserve is situated (16 U.S.C.A. § 500) shall be expended as follows: Seventy-five percent for the public schools and twenty-five percent for roads in the counties in which national forests are situated. The funds shall be used to aid in maintaining the schools and roads of those school districts that lie or are situated partly or wholly within or adjacent to the national forest in the county. The distribution to each county from the proceeds received on account of a national forest within its boundaries shall be in the proportion that the area of the national forest in the county bears to the total area of the forest in the state, as of June thirtieth of the fiscal year for which the money is received.