Section 7. 20 departments. All executive and administrative offices, boards, bureaus, commissions, agencies and instrumentalities of the executive branch (except for the office of governor, lieutenant governor, secretary of state, attorney general, superintendent of public instruction, and auditor) and their respective functions, powers, and duties, shall be allocated by law among not more than 20 principal departments so as to provide an orderly arrangement in the administrative organization of state government. Temporary commissions may be established by law and need not be allocated within a department.