(dissenting.) The defendant seeks to establish the defense-of payment by showing a paroi agreement between the plaintiff and tenant under which the plaintiff was to take certain improvements and fixtures made by the tenant upon the demised premises, the value of which were to apply on the last installment of rent to fall due under the lease. This evidence was-objected to by the plaintiff on the ground that the contract reduced to writing was the best evidence, and that all conversations prior to and at the time of making the lease were merged in the writing, and could not be used as a defense by the surety. The ruling was reserved by the referee, and the evidence-received subject to plaintiff’s motion to strike out. The evidence tended to-establish the agreement that the improvements and fixtures put upon the demised premises by the tenant during his term should be taken by the plaintiff, and their value applied upon the last installment of rent, and that their value was $116.02. The case discloses that. At the conclusion of the evidence the plaintiff moved to strike out all of the evidence to the alleged agreement on the part of the plaintiff to buy any property of J. W. Farrington, or take any of the property or fixtures he had put in the premises, if he would take-a lease of the building for another year, and to strike out all testimony of the value of the property. The referee granted the motion, and struck out all such evidence, and the defendant excepted to his ruling. The defendant insists that this was error for which the judgment should be reversed. It is-quite clear that, if the fixtures and improvements made by the tenant would have been a good defense or payment as to him, they would inure to the-benefit of the surety when he is asked to pay the principal debt. Baere v. Armstrong, 26 Hun, 19. The surety upon a lease for the payment of rent can make any defense to the action against him for rent that the tenant could make. Sheary v. Adams, 18 Hun, 181. This i§ not in the nature of a right, of action arising solely in favor of the tenant, of which the surety, when sued alone, could not avail himself. Springer v. Dwyer, 50 N. Y. 22; Lasher v. Williamson, 55 N. Y. 619. If the value of the fixtures and improvements, are available to the tenant for any purpose, they are payments upon the-last installments of rent, and reduce or extinguish alike the liability of. the lessee and surety. Was the paroi evidence of the paroi agreement competent in this case? The rule is too well settled to require the citation of authorities that, where the written contract is or purports to be complete upon its face, containing the stipulations of both parties, it cannot be altered, modified, or varied by any prior or contemporaneous paroi agreement between the parties, and that all such paroi agreements are deemed to be merged in the writing. But this rule does not apply to writings which purport to express only the agreement of one of the parties, or one side of the agreement, (Engelhorn v. Reitlinger, 122 N. Y. 80-82, 25 N. E. Rep. 297, and cases there cited;) nor does it apply to a collateral undertaking, not necessarily a part of the contract. Applying the rules stated in the exceptions to the case under consideration, the evidence offered and excluded would seem to be competent. Johnson v. Oppenheim, 55 N. Y. 280; Wilson v. Deen, 74 N. Y. 531; Eighmie v. Taylor, 98 N. Y. 288; Snowden v. Guion, 101 N. Y 458, 5 N. E. Rep. 322; Schmittler v. Simon, 114 N. Y. 176, 21 N. E. Rep. 162. In the case at bar the certificate of hiring is only made by the tenant, and contains none of the obligations or liabilities assumed by the plaintiff. We must look outside of it for any obligation on the part of the plaintiff for quiet enjoyment, or even any possession at all of the premises. It does not purport on its face to express the contract of the lessor. As his part of the contract is not, therefore, in writing, can it be doubted, under the authorities, that they may be proved by paroi? The certificate shows that the lessee agreed to pay rent. In the absence of any writing as to what the agreement of the lessor was, may not the defendant prove that he agreed to accept improvements and fixtures at their fair value for the amount of that rent? We think he may *455Again, as the plaintiff’s agreement was not reduced to writing, it seems that within these exceptions it would be competent to prove that as an inducement to the lessee to enter into the new lease the lessor might agree by paroi to allow the last installment of rent to be paid in the new improvements on the place. That would be an agreement collateral to the lease, and it would seem competent within the authority of the cases. Batterman v. Pierce, 3 Hill, 172. Nor does the paroi agreement sought to be proved, but excluded by the referee, change the written certificate. It does not relieve the lessee from the payment of rent, or reduce the amount of the same, or change the time of payment. The law would apply the fixtures on the rent at the commencement of the last month, and vest the title to them in the lessor at that time. It is collateral to the certificate, but not in conflict with its provisions. Arms v. Arms, 13 N. Y. St. Rep. 196; Adams v. Van Brunt, 11 N. Y. St. Rep. 659. If we are right in our conclusion as to the evidence of this paroi agreement to accept, the fixtures in payment of a portion of the rent, then the exclusion of this evidence was error prejudicial to the rights of the defendant, as it would be inequitable and unjust to compel the surety to pay this rent, or the part thereof which would be satisfied by the application of the value of the improvements to the payment of the same. Juilliard v. Chaffee, 92 N. Y. 529. This case is clearly distinguishable from Costello v. Eddy, 12 N. Y. Supp. 236. In that case the' contract was signed by both parties, and was complete in itself, and the paroi evidence offered clearly void in its effect; and the court held that it was properly excluded. In this case, for the reasons above stated, we think it was error to exclude the evidence offered, and to strike out the same on the motion of the plaintiff, and, as that ruling prejudiced the legal rights of the defendant, the judgment must for that reason be reversed. This makes it unnecessary to consider the other-questions raised by the appellant on this appeal. I think the judgment should be reversed, referee discharged, and a new trial ordered, costs to abide the event.