The Secretary of the Interior is authorized, in his discretion, to acquire by purchase and/or accept by donation, in behalf of the United States, such lands, easements, and buildings comprising the former Governor Berkeley’s mansion and homestead in James City County and Carter’s Grove mansion and homestead in the same county, and the Rosewell mansion and homestead in Gloucester County as are desirable for the proper rounding out of the boundaries and for the administrative control of the Colonial National Historical Park, and such lands as are necessary for parkways, not to exceed five hundred feet wide, to connect said mansions to the said Colonial National Historical Park, the title and evidence of title to lands acquired to be satisfactory to the Secretary of the Interior: Provided, That the said acquisition of lands and/or improvements shall be made only from such funds as may be appropriated pursuant to the authorization of section 81f of this title.