Where a contract to purchase land is presented to the vendor, signed by the purchaser, it is for the vendor to decide whether the purchase is acceptable, and if he then executes the contract himself, he ratines the act of his agent in having previously, though unauthorizedly, so done, it is binding on him. Flynn v. Jordal, 124 Iowa, 457, 100 N. W. 326; Findlay v. Koch, 126 Iowa, 131, 101 N. W. 766. See also Secs. 24, 620, 622.