Smith owned Blackacre in fee simple absolute. In section 3 of a properly executed will, Smith devised Blackacre as follows:

“I devise my farm Blackacre to my son Darwin so long as it is used as a farm.” Sections 5 and 6 of the will made gifts to persons other than Darwin. The last and residuary clause of Smith’s will provided “All the residue of my real and personal property not disposed of heretofore in this will, I devise and bequeath to Stanford University.” Explain what interests in Blackacre were created by Smith’s will.