On July  3, 1935, Silvestra Lubrico and Sabas M.  Abastillas entered into a contract whereby the former leased to the latter lot No. 933 of the Pontevedra cadastre, containing 22.6405 hectares,  for  the period of  five agricultural years beginning  1936-1937, extendible for another period of fifteen agricultural years at the option of the lessee.  It was stated in the contract that said land "is dedicated to the planting of sugar cane and is registered  in  the La Carlota Sugar Central as a miller with a quota of  about 500 piculs." The stipulations as  to the payment  of the  rent  provide as follows:

"3. El  arrendatario  se  obliga a  pagar  a la Arrendadora, en concepto de alquiler o arriendo,  el  diez  por  ciento (10%) de  la cuota asignada a la parcela de terreno arriba descrita como cuota de exportation, de acuerdo con la orden u ordenes ejecutivas que librare Su Excelencia el Gobernador-General, en definitiva o de año en año, como sea el caso, de tal suerte que si para la cosecha de 1936-37 dicha cuota de exportation se fijare en 500 picos, el Arrendatario pagara a la Arrendadora la cantidad de 50 picos solamente, o, si se rebajare, el 10% de la cuota asi rebajada. Para los efectos de este arrendamiento o alquiler la Central Azucarera de La Carlota, en donde se muele  la  caña-dulce procedente del lote arrendado, queda por el  presente autorizada para que pueda retener y retenga, desde el comienzo de cada molienda, el 10% del  azucar  centrifugado que se produjere semanalmente de la cana-dulce sembrada en el terreno objeto de este arrendamiento, hasta que se cubra el 10% de la mencionada cuota, debiendo entregar directamente  a la Arrendadora, o a su representante debidamente autorizado, los quedanes representatives del referido 10% de arriendo.  *  *  *

"4. Durante la  vigencia de  este contrato  y con tal de que  el Arrendatario pueda  sembrar las partes del terreno arrendado productibles de caña y suficientes para cubrir la cuota asignada, dicho  Arrendatario podra dedicar el resto del terreno  a  cualquiera otra clase de siembra o producto, sin que para ello tenga que participar nada a la Arrendadora de cualesquiera producto o beneficio que obtuviere en dicha parte no sembrada de cana, pues se ha estipulado expresamente que  la Arrendadora no  percibira  cantidad alguna del Arrendatario en concepto  de alquiler del terreno arrendado de todas cualesquier siembras que no sea la cana-dulce."

Said contract was duly registered and annotated on the certificate of title.

On October 23, 1936, the herein plaintiffs bought said lot No.  933 from Silvestra  Lubrico.  In 1937 the herein defendant  Sabas M.  Abastillas and one  Andres  Javier instituted civil case No. 7257 in the Court of First Instance of Occidental Negros against Silvestra Lubrico and the herein plaintiffs Jose Rongo  and Perpetuo Puerto for the foreclosure of a mortgage on another lot which had also been bought by Jose Rongo and Perpetuo Puerto from Silvestra Lubrico, subject to the mortgage.  In that action the defendants in their answer set up a cross-complaint in which, as a first cause of action, they claimed damages against the plaintiff Sabas Abastillas for nonpayment  of the rent on lot No. 9J33 corresponding to  the agricultural years 1935- 1936 and  1936-1937; and, as a  second cause of  action,. prayed for the rescission of said contract of lease  on the alleged ground  of  breach by  the  lessee of the condition thereof regarding the payment of  the rents.  In deciding said case No. 7257 the court absolved the  plaintiffs from the  cross-complaint upon the following finding:

"En cuanto al lote 933 que Sabas Abastillas  tomo en arrendamiento de la  demandada desde el ano agricola de 1935-36, se ha demostrado que no tenia la  cuota de quinientos picos que se menciona en el contrato correspondiente, pero que  ultimamente se le ha podido asignar una cuota de 142.23 picos, diez por ciento de  la cual debe pertenecer a la demandada, y que segun la misma escritura la Central Azucarera de La Carlota esta autorizada a retener para ser entregada  a la arrendadora, y que,  segun Sabas Abastillas, obra en poder de la central a disposition de Silvestra Lubrico."

The defendants did not appeal from  said decision, but nearly two years after its rendition, that is  to say, on July 28, 1939, instituted the present action for the rescission of the said contract of lease and  for damages, alleging among other things the following:

"That after a careful reading of the above-cited contract, the conclusion is clear that the sole and only cause,  consideration or motive which was the principal inducement leading to the agreement and execution of said contract of lease was the fact that Lot No. 933 subject of the lease had a registered quota  of  500 piculs of centrifugal sugar as stated in paragraph 1 of said contract of lease;

"*      *      *      *      *      *      *      *      *      *

"That after the execution of the aforesaid contract of lease and the  defendant had  already  taken possession of the premises, and after the allocation of the quota by the La Carlota Sugar Central, it resulted that said Lot No. 933 did not have any sugar quota, nor did it ever have at all as contemplated by the parties in the aforecited  contract of lease;

"That the parties in the aforesaid contract of lease at the time of  its execution, had in good faith believed that the land subject of the contract had a sugar quota of 500 piculs, and by believing so and agreeing to base the rentals upon the said quota, the parties had made a mistake or error with respect to the substance of the thing, which is the object or subject matter of the contract;

"That a  situation very prejudicial and unequitable to the lessor  (plaintiffs) exists in a way that the lessee (defendant) continued to possess the premises for his sole and exclusive use and benefit without the least participation to the lessor or the owners of the land, who, up to the filing of this complaint, have never received any share or rental from the land leased by the defendant, and that the same situation will become more aggravated by defendant's option of renewal of the lease for another period of fifteen (15) years (paragraph 2, contract of lease)."

The defendant  pleaded res judicata as a defense  and, in a petition supported by the pleadings and a copy of the decision in case No. 7257, asked for a summary judgment in accordance with section 2 of Rule 36.  The court sustained the pleas  and dismissed the  complaint without any  pronouncement as to costs.  Hence this appeal.

Appellants contend that the trial court erred  (1) in sustaining  the plea of  res judicata and  (2)  in granting the petition for summary judgment  without  having tried  the case on the merits.

First.  The plaintiffs are bound  by the finding  of  the court in the previous case that subsequent to the execution of the contract of  lease in question a quota of 142.23 piculs was assigned to lot No. 933, 10% of which ought to correspond to the lessor, and that in accordance with the contract of lease La Carlota Sugar Central was authorized to retain and was retaining that portion of sugar subject to the disposition of the lessor.   In  respect to this matter, which was directly adjudged, the former  judgment is conclusive between the parties.  (Peñalosa vs.  Tuason, 22 Phil., 303; section 44 [b] Rule 39.)   Therefore, the plaintiffs cannot be heard in the present action to say, as they allege in their complaint, that lot No. 933 never had any sugar quota and that they never received any rental from the land leased by the defendant. It is of no avail to the plaintiffs to contend, as they do, that in the previous case the cause of action they alleged for the rescission of the contract of lease in question was the lessee's failure to pay the stipulated rents while in the present case their cause of action for rescission is lack of consideration, i.e., the nonexistence of the expected quota of 500 piculs.   Both of these  so-called causes of action for rescission existed at the time the present plaintiffs filed their cross-complaint in the previous case.  All that should have been but was not alleged then is deemed to have been waived and  cannot be availed of in a subsequent action between the same parties over the same subject matter.  (Peñalosa vs. Tuason, supra.)  It goes without saying that the trial court committed no error  in sustaining the plea of res judicata.

But  regardless of the validity of that plea, we think plaintiffs' action  could not  prosper in any event upon the facts alleged in their complaint. The burden of their contention, as we gather it from their complaint and from their brief in this  Court, is  that the contract of lease  in  question is one- sided and highly disadvantageous to the lessor because the quota  assigned to the land leased  turned out to be only 142.23 piculs, and 10 % of that is  only 14 piculs a  year, which  is utterly inadequate to compensate the use and occupation by the lessee of  22½ hectares of agricultural land which, according to  the plaintiffs, is capable of producing 400  cavans of palay  and 1,000 piculs of  sugar a year.  But the stipulation in the contract on this point, which we have hereinbefore set forth, constitutes  a valid consideration; and  in the absence of any allegation that the lessor was not of sound  mind at the time she entered into said contract, or that she signed it thru force, intimidation, or fraud, the court is powerless to relieve her from her obligation however much it may sympathize with her in her plight. The plaintiffs  bought the land from her and assumed the lessor's obligation with full knowledge of its terms and conditions. The allegation that the parties made a mistake with respect to the substance of the thing in that they believed said land had a sugar quota of 500 piculs, is but a conclusion of fact which  is belied by the stipulation in the contract that the lessee shall pay to the lessor  10% of the quota for export sugar' that may be assigned in accordance with the order of the  Governor-General from year to year, "so that if the export quota for 1936-1937 be fixed at 500 piculs the lessee shall pay to the lessor 50 piculs, or if it be reduced, 10% of the quota as reduced."

As a matter of fact, in bringing an action for rescission the plaintiffs  impliedly recognize  that the contract sought to be rescinded was validly entered into.  Article 1290 of the Civil Code says that contracts validly entered into may be rescinded  in the cases established by law.   Those cases are indicated  in articles 1291  to 1298; but the case for the plaintiffs does not fall within any one of those articles.  On the contrary,  article  1293 provides  that no contract  shall be rescinded  for lesion excepting those mentioned in paragraphs 1 and 2 of article 1291; that is to say, those entered into by guardians without the authorization of the family council  and those executed in representation  of absentees. The contract in question does not fall within either of these provisions.

However, we are bound to take notice of current history and cannot ignore the fact of  common knowledge that subsequent to the rendition  of the judgment appealed from and since  the agricultural year 1942-1943, the sugar quotas for exportation from the Philippines have disappeared. For that reason it would now seem impossible to determine the amount of the rent under the  contract of lease in  question. But we cannot base our decision upon such subsequent historical fact and declare said contract extinguished for impossibility  of performance,  because that  is  not within the issues submitted to us for decision and the parties have not been heard on that matter.  We merely  make the observation so that our judgment may not be interpreted as affirming that the plaintiffs are bound  by  the  contract in question for the rest of the fifteen-year period therein stipulated regardless of the abolition or disappearence of the sugar quota for exportation.  Is it perchance much to hope that,  as  become good  neighbors  and honorable and fair-minded men, the parties will  amicably  settle their differences, modifying their agreement as to the rent in view of the new and unforeseen situation that has  arisen, thereby avoiding further litigation for the sake  of social amenities and of their own economic interests?  It is the duty of counsel to strive for that settlement.

Second.  The summary judgment rendered by the trial court  was a judgment on the merits and was permitted by Rule 36, inasmuch as there was no genuine issue as to any material fact and the question involved  was purely one of law.

The judgment is affirmed, with the costs of this instance against the appellants.  So ordered.

Yulo, C.J., Moran, Paras, and Bocobo, JJ.,  concur.