“ If no such order of succession is in effect at that time, then such officers shall act as Secretary in the descending order of rank, as established by the listing of their offices in Sections 5314, 5315 or 5316 of Title 5 of the United States Code and, at each level of the Executive Schedule, in the order in which they shall have taken oath as such officers. ”

“ During any period when, by reason of absence, disability, or vacancy in office, both the Secretary of Agriculture and the Deputy Secretary of Agriculture are not available to exercise the powers or perform the duties of the Office of Secretary, the officers from the Department of Agriculture whose appointments are vested in the President, by and with the advice and consent of the Senate, shall act as Secretary in such order as the Secretary of Agriculture may from time to time prescribe. ”