middle lamella

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.