13. Every warehouse-man shall exercise such care to keep in his warehouse the agricultural produce of different depositors separate from each other so as to permit, at all times, the identification of the ownership and quality of such produce deposited and to facilitate easy delivery of such produce on demand by depositors: Provided that where standardised and graded agricultural produce is stored in a warehouse, subject to any agreement between the warehouse-man and a depositor, there may be pooling of the same variety of such produce belonging to several depositors and each depositor shall be entitled only to his portion of such produce according to weight or quantity, as the case may be, as shown in his receipt.