A phyllome anlagen (PO:0025430) that will give rise to a vascular leaf primordium (PO:0000017) and is part of a peripheral zone (PO:0000225) of a shoot apical meristem (PO:0020148). [source: PMID:14732442, POC:Laurel_Cooper]
Comment
This is the region where you have the maximum concentration of auxin in the SAM (at least in a few species that have been studied).