The first-formed layer of the primary wall (see cell wall
) formed from the *phragmoplast
. Compounds of pectic acid, e.g. calcium and magnesium pectates, are deposited into the cavities of the phragmoplast and these eventually coalesce to form a continuous opaque layer. Cellulose molecules, organized to form *microfibrils
, are deposited to build up the primary wall. In mature tissues the middle lamella cements the walls of contiguous cells.