The secretary of state shall be ex officio register of the state land office. The books and records of such office shall be so kept as to show and preserve an accurate chain of title from the general government to the purchaser of each smallest subdivision of land; to preserve a permanent record, in books suitably indexed, of all correspondence with any of the departments of the general government in relation to state lands; to preserve, by proper records, copies of the original lists furnished by the selecting agents of the state, and of all other papers in relation to such lands which are of permanent interest.