Section 20. Money declared by written instrument to be intended for perpetual care, maintenance, improvement or embellishment of any cemetery, or of any lots or plots therein, to an amount not less than two hundred dollars, may be deposited with the state treasurer, who shall receive and receipt for it in the name of the commonwealth. The depositors at the time of making such deposit shall file with him and with the state secretary a copy of such instrument. If the cemetery belongs to a corporation, the deposit shall be accompanied by a written agreement, signed by the president thereof, to the effect that it will accept the income derived from the fund so deposited, and will apply it to the purposes set forth in the instrument. Upon the receipt of a deposit for the perpetual care of individual lots or plots in public burial places or cemeteries, the state treasurer shall so inform the clerk of the city or town in which they are located, and said clerk shall record the facts relating to said deposit in the margin of his records of said lots or plots.