The treasurer of any such district shall, when directed by resolution of the board, invest such guaranty fund, and the income thereof, in the United States government bonds or municipal bonds approved for savings bank investment in the states of New York and Massachusetts, so that the same may always be readily convertible into cash if and when needed for the purposes in this act N.M. Stat. Ann. § 73-16-41 to 73-16-49 provided.