Name the layer of cementing material which holds adjacent plant cells. Where is it lacking ?

Explanation

**Step-by-Step Solution:**

1. **Identify the Layer of Cementing Material:**
- The layer of cementing material that holds adjacent plant cells together is called the **middle lamella**. It acts as a glue that binds the cells.

2. **Understanding the Function of the Middle Lamella:**
- The middle lamella is primarily composed of pectins, which are polysaccharides. This layer is crucial for maintaining the structural integrity of plant tissues by holding cells together.

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