In an action by a broker for commissions, evidence of independent negotiations regarding an option after a sale had been completed by plaintiff is inadmissible, though it might have been competent if relating to negotiations before the sale was made. Reed v. Light, 170 Ind. 550, 85 N. E. 9; Geo. B. Loving Co. v. Hesperian Cattle Co., 176 Mo. 330, 75 S. W. 1095.