"Where, in an action by a broker for commissions in procuring a purchaser for a tract of land, it appeared that the contract of employment only fixed the price, and that the broker executed a contract of sale binding the owner to furnish an abstract of title, an instruction that if the owner entered into the contract by which he authorized the broker to sell the land at the price named, and the broker entered into a contract for the sale thereof at the price named, to a person ready, able and willing to pay therefor, he was entitled to his commissions, was erroneous, on the issue whether the sale made by the broker was on the terms on which he was authorized to effect a sale. Hunt v. Tuttle, 133 Iowa, 647, 110 N. W. 1026. See references under Sec. 307.