7 U.S.C. § 2268a

1. (a)The Department of Agriculture is authorized to acquire land, or interest therein, by purchase, exchange or otherwise, as may be necessary to carry out its authorized work: Provided, That no acquisition shall be made under this authority unless provision is made therefor in the applicable appropriation or other law.
2. (b)Appropriations for the Department of Agriculture which are available for the purchase of land may be expended for options to purchase land: Provided, That not to exceed $1 may be expended for each option to purchase any particular tract or tracts of land unless otherwise provided in appropriation or other law.