Under a written agreement of a land owner to pay a. broker a certain sum if he should send or cause to be sent to the land owner a person with whom the latter "may see fit and proper to effect a sale or exchange of the land," the broker can not recover the sum stipulated without proof of the sale or exchange of the land, nor on a quantum meruit for services in negotiations for such sale or exchange, without proof that such negotiations were rendered fruitless by the fault of the land owner.

Walker v. Tirrell, 101 Mass. 257; Drury v. Newman, 99 Mass. 256; Robinson v. Okl. Fire Ins. Co., 155 P. 202, - Okl. Sup. - .