321.15  Highway patrol; pensions and pension trust fund.--There is hereby created and established a continuing fund to be known as the "Highway Patrol Pension Trust Fund." Such fund shall be made up from contributions from members (employees) of the Department of Highway Safety and Motor Vehicles who have subscribed to the constitutional oath of office, and from a yearly sum to be paid into such fund from the appropriation of the department in such an amount as shall be sufficient to carry out the provisions of this law. Such state funds shall not be less than the yearly contribution paid by all members.