The Secretary of the Interior is authorized, in his discretion and upon submission of evidence of title satisfactory to him, to accept, on behalf of the United States, title to the lands referred to in as may be deemed by him necessary or desirable for national-park purposes: , That no land for the Big Bend National Park shall be accepted until exclusive jurisdiction over the entire area, in form satisfactory to the Secretary of the Interior, shall have been ceded by the State of Texas to the United States.section 156 of this titleProvided