In an action for partition, the superior court may, in its discretion, upon motion of any party to the action, order the whole premises sought to be divided, or any particular lot, portion, or tract thereof or the interest of the plaintiff or plaintiffs or of the defendant or defendants in the whole premises, or in any particular lot, portion, or tract thereof, to be sold, either at public auction or by private contract, under the direction of the court, by the commissioner or commissioners appointed to divide or sell the same; provided, that if the sale is made by private contract, it shall not be made for less than the sum fixed by the court in its decree authorizing the sale by private contract.