Functions of all officers of Department of the Treasury and functions of all agencies and employees of such Department transferred, with certain exceptions, to Secretary of the Treasury, with power vested in him to authorize their performance or performance of any of his functions, by any of those officers, agencies, and employees, by Reorg. Plan No. 26 of 1950, §§ 1, 2, eff. July 31, 1950, 15 F.R. 4935, 64 Stat. 1280, 1281, set out in the Appendix to Title 5, Government Organization and Employees. Collecting officers, referred to in this section, are officials of Department of the Treasury.