On the basis of variation in form, structure and development sclerenchyma cells are of how many types?

Answer

**Step-by-Step Solution:**

1. **Understanding Sclerenchyma**: Sclerenchyma is a type of simple permanent tissue found in plants. It is characterized by cells that have thick, hard, and lignified walls. These cells are typically dead at maturity due to the loss of protoplast.

2. **Types of Simple Permanent Tissues**: There are three main types of simple permanent tissues in plants: parenchyma, collenchyma, and sclerenchyma. Here, we focus on sclerenchyma.

3. **Variation in Sclerenchyma Cells**: Sclerenchyma cells can vary in form, structure, and development. Based on these variations, sclerenchyma cells are classified into two main types.

4. **Identifying the Types**: The two types of sclerenchyma cells are:
- **Fibers**: These are elongated cells that provide strength and rigidity to the plant. They can withstand various strains and stresses. Common examples include fibers obtained from jute, flax, and hemp.
- **Sclereids (or Sclerotic Cells)**: These cells are more polyhedral in shape and can be columnar or branched. They have very thick walls and narrow cavities, and are typically found in the fruit walls of nuts and in the pulp of fruits like guava and sapota.

5. **Conclusion**: Therefore, on the basis of variation in form, structure, and development, sclerenchyma cells are classified into two types: fibers and sclereids.

**Final Answer**: Sclerenchyma cells are of two types.

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