The county treasurer of the county in which is located any portion of the lands of the district shall be and he is hereby constituted ex-officio district treasurer of the district extending into his county, and the said county treasurer shall be liable upon his official bonds to indictment and criminal prosecution for malfeasance, misfeasance or failure to perform any duty herein prescribed, as county treasurer or ex-officio treasurer, as provided by law in either case as county treasurer.