Unless a decedent shall otherwise direct by will, the federal estate tax imposed upon decedent's estate, shall be apportioned among all of the persons, heirs and beneficiaries of decedent's estate who receive any property which is includable in the total gross estate of said decedent for the purpose of determining the amount of federal estate tax to be paid by said estate, Provided, That no part of the federal estate tax shall be apportioned against property which, in the absence of any apportionment whatsoever, whould qualify for any charitable, marital or other deduction or exemption, nor against recipients of such property on account thereof.
IC 29-2-12-2