No law shall be passed except by bill, and no bill shall be so amended in its passage through either house as to change its original purpose.
Tex. Const. art. 3, § 30, under Legislative Department.
Tex. Const. art. 3, § 30
LAWS PASSED BY BILL; AMENDMENTS CHANGING PURPOSE PROHIBITED
No law shall be passed except by bill, and no bill shall be so amended in its passage through either house as to change its original purpose.