Any person interested in the parcel may redeem it within one year after the date of sale, by paying to the county treasurer for the purchaser a sum equal to the purchase price stated in the certificate with interest thereon at the rate of 11/2percent per month from the date of sale to that redemption, either in whole or in part, in cash or in bonds of the district, or their interest coupons, issued on the assessment and then matured, or to mature within 60 days from the date of payment.