A lienholder who has contributed to the erection, alteration, removal, or repair of two or more buildings or other improvements situated upon or removed to one lot, or upon or to adjoining lots, under or pursuant to the purposes of one general contract with the owner, may file one statement for the entire claim, embracing the whole area so improved; or, if so electing, the lienholder may apportion the demand between the several improvements, and assert a lien for a proportionate part upon each, and upon the ground appurtenant to each, respectively.