Where a tenant adds fixtures to the premises which are removable, they must be removed by him at or before the expiration of his tenancy; otherwise the tenant is assumed to have waived his right to remove them. If the tenant has made improvements which he is entitled to remove, and thereafter, upon the expiration of his tenancy, he enters into a new lease with the landlord without reserving the right to remove the improvements, he is assumed t6 have waived his right and cannot thereafter enforce it.