(a)
Except as provided in subdivision (b), if an appointment by will or by instrument effective only at the death of the donee is ineffective because of the death of an appointee before the appointment becomes effective and the appointee leaves issue surviving the donee, the surviving issue of the appointee take the appointed property in the same manner as the appointee would have taken had the appointee survived the donee, except that the property passes only to persons who are permissible appointees, including appointees permitted under
Section 674. If the surviving issue are all of the same degree of kinship to the deceased appointee, they take equally, but if of unequal degree, then those of more remote degree take in the manner provided in Section 240.
(b)
This section does not apply if either the donor or donee manifests an intent that some other disposition of the appointive property shall be made.