Tex. Water Code § 62.307: ANNEXATION OF WHOLE OF ADJACENT COUNTY.

If the territory included inside the boundaries of the annexing district consists of all of a single county and the territory to be annexed consists of all of an adjacent county, the adjacent territory may be annexed in the manner provided in Sections 62.291-62.306 of this code, except the commissioners court of the county to be annexed shall:

(1) conduct the hearing;

(2) order the election;

(3) canvass the returns of the election; and

(4) perform all other duties provided by this subchapter for the commission of the annexing district.

Acts 1971, 62nd Leg., p. 110, ch. 58, Sec. 1, eff. Aug. 30, 1971.