Section 15. The state treasurer may receive from the trustees of Massachusetts training schools the principal of the various trust funds conveyed or bequeathed to the said trustees for the use of any institution of which they are trustees; and upon the request of said trustees he shall pay out the income of all such funds, and such part of the principal as may be subject to the control of said trustees, in such manner as the trustees may direct, subject to any condition affecting the administration thereof. The state treasurer may also receive from said trustees the unclaimed money paid over under section twenty-three A of chapter one hundred and twenty which shall be held by him as a single fund, the income of which shall be expended as directed by said trustees for the purpose of securing special training or education for or otherwise aiding and assisting their meritorious wards. Upon certificate of the comptroller that a claim thereto satisfactory to him shall have been established and approved in writing by the attorney general, the state treasurer shall pay to any former ward, or to his legal representatives in case of his death, the amount of money held for his benefit and paid over to the state treasurer under said section twenty-three A without any accumulations accruing thereto after such payment over, out of the principal of the fund in which the money so claimed was held as aforesaid. The said funds, if in cash, shall be invested safely by the state treasurer, or, if in securities, he may hold them in their original form or, upon the approval of the governor and council, sell them and reinvest the proceeds in securities which are legal investments for the commonwealth sinking funds. He shall be held responsible for the faithful management of said trust funds in the same manner as for other funds held by him in his official capacity.