When the veinlets form network the venation is known as

Answer

**Step-by-Step Solution:**

1. **Understanding Venation**: Venation refers to the pattern of veins in the leaves of plants. It is crucial to recognize that the arrangement of these veins can vary significantly among different plant species.

2. **Identifying Types of Venation**: There are two primary types of venation:
- **Parallel Venation**: In this type, the veins run parallel to each other and do not form a network.
- **Reticulate Venation**: This type occurs when the veinlets form a network or a web-like structure.

3. **Defining Reticulate Venation**: When the veinlets in a leaf form a network, this pattern is specifically referred to as "reticulate venation". This means that the main vein divides into smaller branches (veinlets) that interconnect, creating a net-like appearance.

4. **Types of Reticulate Venation**:
- **Unicostate (Finite)**: This type has a single main vein that branches out into veinlets, creating a network.
- **Multicostate (Palmate)**: This type features multiple principal veins that extend from a single point, also forming a network.

5. **Conclusion**: Therefore, when the veinlets form a network, the venation is known as "reticulate venation".

**Final Answer**: Reticulate venation.

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