Any preferred or special stock of any class or of any series thereof may be made convertible into, or exchangeable for, shares of any other class or classes or of any other series of the same or any other class or classes of stock of the corporation at such price or prices or at such rates of exchange and with such adjustments as shall be stated and expressed or provided for in the articles of incorporation, or in any amendment thereto, or in the resolution or resolutions providing for the issue of such stock adopted by the board of directors as provided in section 91 of this title.