Whenever an association organized hereunder with preferred capital stock shall purchase the stock or any property, or any interest in any property of any person, firm, or corporation or association, it may by agreement with the other party or parties to the transaction discharge the obligations so incurred, wholly or in part, by exchanging for the acquired interest shares of its preferred? capital stock to an amount which at par value would equal a fair market value of the stock or interest so purchased, as determined by the board of directors. In that case the transfer to the association of the stock or interest purchased shall be equivalent to payment in cash for shares of stock issued. (1921, c. 87, s. 18; C.S., s. 5259(z).)