At the time and place fixed for the hearing on the petition or at any adjournment thereof, the county legislative authority must hear the petition and receive such evidence as it may deem material in favor of or opposed to the formation of the proposed cemetery district or to the inclusion or exclusion of any lands in the proposed district, but no lands not within the boundaries of the proposed district as described in the petition may be included without a written waiver describing the land, executed by all persons having any interest of record therein, having been filed in the proceedings. No land within the boundaries described in the petition may be excluded from the proposed district.