When any land, other than lands occupied and used in connection with state institutions, owned or held by the state within incorporated cities, towns, diking, drainage or port districts in this state, against which local improvement assessments have been paid, as herein provided for, is offered for sale, there shall be added to the appraised value of such land, as provided by law, such portion of the local improvement assessment paid by the state as shall be deemed to represent the value added to such lands by such improvement for the purpose of sale, which amount so added shall be paid by the purchaser in cash at the time of the sale of said land, in addition to the amounts otherwise due to the state for said land, and no deed shall ever be executed until such local improvement assessments have been paid, and nothing herein shall be construed as canceling any unpaid assessments on the land so sold by the state, but such land shall be sold subject to all assessments unpaid at the time of sale.