An anther wall secondary parietal cell layer (PO:0006007) that is formed towards the inside, after the cells of an anther wall primary parietal cell layer (PO:0006006) undergo a periclinal division. [source: GR:Pankaj_Jaiswal, ISBN:9780003686647, PMID:2476454]
Comment
In many angiosperms, including Arabidopsis, it divides periclinally to form an anther wall middle layer externally and an anther wall tapetum internally. Alternatively, it may differentiate into a tapetum.