The State Forestry Commission is hereby authorized and it shall have the power to supply from its forest tree nursery or nurseries such forest tree seedlings and transplants as may be necessary and suitable for reforesting any part or all of any lands so acquired or now owned and so administered by any such county, city, or town and to furnish such technical assistance and supervision as the said State Forestry Commission may deem necessary for the proper management and administration of such lands and forest thereon free of cost to the counties, cities, and towns; provided, that the respective counties, cities, and towns shall agree to administer such lands in accordance with the practices and principles of scientific forestry as determined by said State Forestry Commission.