The correct answer is option 4: plants.

A cellulosic wall refers to the presence of cellulose in the cell walls of a particular type of organism. Cellulose is a complex carbohydrate that provides structural support to the cell walls of plants.

Option 1: Animals - Animals do not have cellulosic walls. Instead, they may have different types of cell walls or no cell walls at all.

Option 2: Bacteria - Bacteria do not have cellulosic walls. Their cell walls can be classified into different types, such as peptidoglycan or lipopolysaccharide.

Option 3: Fungi - Fungi have cell walls, but their cell walls mainly consist of a substance called chitin, not cellulose.

Therefore, the correct answer is option 4: plants, as cellulosic walls are specifically found in the cells of plants.