When the defendant claims allowance for improvements, the plaintiff may by entry on the record require that the value of his estate in the premises without the improvements shall also be ascertained. The value of the premises in such cases shall be estimated as it would have been at the time of the inquiry, if no such improvements had been made by the tenant or any person under whom he claims, and shall be ascertained in the manner hereinbefore provided for estimating the value of improvements. (1871-2, c. 147, ss. 10-11; Code, ss. 482, 483; Rev., ss. 661, 662; C.S., s. 705.)