I've of course done the obligatory goggling and looking at images but it's all inconclusive and seems to depend on wood type and age.
As I know nothing on trees here is some additional info that may or may not be useful.
Type is Bramley apple also referred to as cooking apples, very low sugar content, taste horrible if you eat them off the tree.
The log is about a foot across and it fell down last august, so have seasoned for the best part of a year
I would be inclined to think that the heartwood starts by the red arrow but not sure, would suck if it was the blue one as that would only give me a handful of sticks rather than years worth of supply
Without much more ado this is one of the crosscuts that i have from my fallen Apple tree.

Let me know what you think, educated guess or otherwise, any help would be appreciated.
Cheers