Collenchyma cells are the simple permanent tissue that provides support and structure. Their thick cell walls are composed of the compounds of cellulose and pectin. Cells of collenchyma lack secondary walls, and the hardening agent "lignin" is absent in their primary walls. 
So, the correct answer is 'Collenchyma.'

**Collenchyma**

Collenchyma is a type of simple mechanical tissue found in plants. It is characterized by its elongated and living cells with thickened cell walls. The primary function of collenchyma is to provide support and flexibility to growing plant parts.

**Structure and Characteristics of Collenchyma**

Collenchyma cells have several distinct features that make them suitable for their role in providing mechanical support:

1. **Cell Shape**: Collenchyma cells are elongated and have irregularly thickened cell walls. These thickened areas are known as thickenings or the primary cell wall.

2. **Living Cells**: Unlike sclerenchyma cells, which are dead at maturity, collenchyma cells are living cells. This allows them to provide support to growing plant parts.

3. **Variable Cell Wall Thickness**: The primary cell wall of collenchyma cells is unevenly thickened. This thickening can occur at the corners of the cells, along the cell walls, or in localized areas of the cell. The thickened cell walls provide strength and support to the tissue.

4. **Cell Arrangement**: Collenchyma cells are often arranged in strands or cylinders beneath the epidermis of stems and petioles. This arrangement provides support to the plant and prevents it from collapsing.

**Functions of Collenchyma**

1. **Mechanical Support**: Collenchyma tissue provides mechanical support to growing plant parts. The thickened cell walls provide strength and flexibility, allowing the plant to withstand mechanical stress.

2. **Flexibility**: The living nature of collenchyma cells allows them to adapt and stretch as the plant grows. This flexibility is essential for the elongation and bending of plant parts.

3. **Protection**: Collenchyma tissue can also provide protection to delicate tissues beneath it. The thickened cell walls act as a barrier against external mechanical damage.

**Conclusion**

In conclusion, a simple mechanical tissue devoid of lignin is collenchyma. Collenchyma cells have thickened cell walls, variable in thickness, and are living cells. They provide mechanical support and flexibility to growing plant parts.