In an action for commissions for procuring a contract for a lease, defendant might show as against the plaintiff by parol, that the contract was merely provisional, did not express all the terms of the lease to be entered into between the parties, as was also understood by plaintiff, and that the lease was never consummated, because no final agreement was ever made between defendant and the lessee. Buxton v. Beal, 49 Minn. 230, 51 N. W. 918; Crombie v. Waldo, 137 N. Y. 129, 32 N. E. 1042, 33 N. E. 744; Laws v. Schmidt, 80 Ohio St. 108, 88 N. E. 319.