The commission, acting through the Secretary of the Interior, is authorized to receive gifts and contributions from States, Territories, societies, organizations, and individuals for the said Fredericksburg and Spotsylvania County Battle Fields Memorial: Provided, That all contributions of money received shall be deposited in the Treasury of the United States and credited to a fund to be designated “Fredericksburg and Spotsylvania County Battle Fields Memorial fund”, which fund shall be applied to and expended under the direction of the Secretary of the Interior for carrying out the provisions of sections 425 to 425j of this title.