Section 4. Within ten days from the recording of such order, plan and estimate, the board shall cause to be filed in the superior court of the county in which such proposed public improvement or the major part thereof is situated a petition on behalf and in the name of the body politic undertaking such improvement, to establish its right to take the property described in the order and, if betterments are to be assessed, to assess the same on account of the special benefits to be derived from the improvement, and to determine the compensation and damages to be paid, the area to be assessed and the amount of the benefits to be made the basis of assessments. The petition shall contain a copy of the order and estimates, and shall designate the registry or registries of deeds in which the order, plan and estimate have been recorded as provided in section three. The proceeding thus instituted shall be in rem against the land to be taken, damaged or assessed, but every person appearing of record to have an interest in any of said land at the time of the adoption of the order shall be made a party respondent. The court shall issue an order of notice to all of said respondents, returnable at any return day which occurs thirty days or more after the filing of the petition, which shall be served upon all respondents who are residents of the commonwealth or can be found therein in the manner prescribed for serving a writ of summons in civil actions, and upon all other parties by posting a copy thereof on each parcel of land to be taken, damaged or assessed and by sending a copy thereof by registered mail to each of said parties whose address is known, at least twenty days before said return day. Persons not in being, unascertained or unknown who may have an interest in any of such land shall be made parties respondent by such description as seems appropriate, and service may be made on such persons by publication, in such manner as the court may order.