There's never an end to surprises when I return to Nabokov.
I was re-reading certain lines of Shade's poem: " And from the inside,
too, IŽd duplicate/ Myself, my lamp, an apple on a plate:/Uncurtaining
the night, IŽd let dark glass/ Hang all the furniture above the
grass..." and suddenly Shade's apple on a plate glared at me. 
Why would Shade mention an apple right at the start of "Pale Fire", as a
part of his familiar surroundings when, later, we find Kinbote writing
that:  "Shade said that with him it was the other way around: he must
make a definite effort to partake of a vegetable. Beginning a salad, was
to him like stepping into sea water on a chilly day, and he had always
to brace himself in order to attack the fortress of an apple." ?