All evidences of indebtedness pledged to secure scrip shall be delivered and held by the corporation issuing such scrip in trust to secure the redemption thereof in legal tender. All bank deposits securing scrip shall be assigned to such issuing corporation and by it held in trust as herein provided, but the interest and income on such pledged securities and on one-third of such assigned bank deposits may be used to defray the expenses of such corporation and to create a reserve and surplus for future expenses and redemption of scrip.