The taxes imposed by this chapter upon individuals shall apply to the income of estates or of any kind of property held in trust, including:
(1) income accumulated in trust for the benefit of unborn or unascertained person or persons with contingent interests, and income accumulated or held for future distribution under the terms of the will or trust;
(2) income which is to be distributed currently by the fiduciary to the beneficiaries, and income collected by a guardian of an infant which is to be held or distributed as the court may direct;
(3) income received by estates of deceased persons during the period of administration or settlement of the estate; and
(4) income which, in the discretion of the fiduciary, may be either distributed to the beneficiaries or accumulated.