A portion of meristem tissue (PO:0009013) beneath a meristem L2 layer (PO:0009021) in a shoot apical meristem (PO:0020148) which gives rise to internal tissues of leaf and stem. [source: GR:Pankaj_Jaiswal, PMID:11283725, PMID:12221985, POC:Laurel_Cooper]
Comment
The meristem L3 layer cells frequently divide in various orientations.