When the plaintiff commences an action of ejectment, the defendant shall counterclaim for the value of the improvements made upon the land by him or her or by those under whom he or she claims, if he or she or his or her predecessors in title purchased the land recovered in the action, supposing the title to be good in fee at the time of the purchase, or if he or she or his or her predecessors in title took a lease of the land supposing that lease to convey the title and interest therein expressed at the time the lease was accepted. Recovery on the counterclaim shall be contingent on the plaintiff's recovery on the claim for ejectment. The increase in the value of the land in consequence of betterments so made shall be held to be the value of the betterments. (Amended 1971, No. 185 (Adj. Sess.), § 131, eff. March 29, 1972.)