What is a offset ? Give examples.

Explanation

### Step-by-Step Text Solution

1. **Definition of Offset**: An offset is a sub-aerial modification of the stem. This means that it is a type of stem structure that grows just above the ground level, allowing the plant to propagate and spread.

2. **Characteristics of Offsets**: Offsets are typically characterized by short internodes, which are the sections of the stem between two nodes. In the case of offsets, the distance between the nodes is reduced, leading to a compact structure.

3. **Examples of Offsets**:
- **Pistia**: Commonly known as water lettuce, this aquatic plant has offsets that grow laterally from the main stem. Each offset has a rosette of leaves above and a cluster of roots below.
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