Section 27. The petition may be filed with the recorder, or with the assistant recorder at the registry of deeds for any district where the land, or any part thereof, lies. Upon filing his petition, the petitioner shall forthwith cause to be filed in the registry of deeds for each district where any part of the land lies a memorandum stating that the petition for registration has been filed, the date and place of filing, and a copy of the description in the petition of the land or of so much thereof as is within the district. Such memorandum shall be recorded and indexed by the register with the records of deeds. Each assistant recorder shall also keep an index of all petitions in his district, and in every case where the petition is filed with him shall transmit the petition, the papers and plans filed therewith and such memorandum, when recorded, to the recorder.