The following description best fits which simple tissue: walls of alternating pectin and cellulose, may contain chloroplasts at maturity walss thickened in the corners?

Parenchyma
Aerenchyma
Sclerenchyma
Collenchyma
Periderm

Collenchyma

The description provided best fits the simple tissue called "collenchyma." Collenchyma tissues have walls that consist of alternating layers of pectin and cellulose, and their walls are thickened at the corners. It is important to note that collenchyma tissues may also contain chloroplasts at maturity.