May not be grafted. What kind of lemon and where did you get it? Meyers are often rooted from cuttings for the northern market.

Is all the foliage the same?

All those stubs should be removed. Cuts should be flush with the branch collar.....IOW, completely unobtrusive.

I also see no sign of any graft.

As long as I remember,its grafted Eureka lemon tree.Foliage was different for one branch , so I cut that one and the one at the same level.If graft was under soil would roots grow from it?Sorry silly questions but I am new to gardening.

it could be that some of the rootstock genes came through

Rootstock Genes can't pass through the graft genetically. The scion will always stay the same. However the rootstock may push a sweeter fruit with more flavors.

Steve

that's not what heard