Although the plaintiff declared on an express contract to pay him all that he could sell a tract of land for over a certain sum, he may recover on the further allegation of an express promise of defendant to pay him a certain percentage commission, where the broker said he was in the habit of receiving five per cent. commission on sales, to which the defendant did not dissent. Armstrong v. Cleveland, 32 Tex. Civ. App. 482, 74 S. W. 789; Bab v. Hirschbein, 12 N. Y. S. 730.