All departments and institutions of the State may assist in the selling of United States savings bonds to their employees and such assistance shall include the making of deductions from their payrolls in such amounts as may be voluntarily authorized by the employees. Deductions so authorized by any employee, under this provision, shall be held in the State Treasury to the credit of the account of the employee until a sum sufficient to purchase one or more bonds is reached. The head of the department shall then purchase one or more bonds and deliver the same to the employee, in lieu of payment otherwise to the extent of the deduction authorized.