The county mayor of the county in which the larger or largest percent of the lands of such improvement district lies shall be chair of such board of directors, with authority to call meetings of the board. The board shall elect one (1) of the appointed directors secretary and treasurer of the board of directors, and such treasurer shall give bond, as provided by part 6 of this chapter, such bond or a duplicate of same to be filed with the county clerk in each of the counties and recorded in the drainage record, the bond to be taken before and approved by the county court of the county in which the larger or largest percent of the lands of the district lies.