The Secretary of Agriculture may make such rules and regulations as may be deemed advisable to carry out the provisions of this chapter and may cooperate with any department or agency of the Government, any State, Territory, District, or possession, or department, agency, or political subdivision thereof, or any person; and may call upon any other Federal department, board, or commission for assistance in carrying out the purposes of this chapter; and shall have the power to appoint, remove, and fix the compensation of such officers and employees not in conflict with existing law and make such expenditure for rent, outside the District o