Sieve cells are most commonly found in the lower vascular plants.

Answer

To determine whether the statement "Sieve cells are most commonly found in the lower vascular plants" is true or false, we can analyze the information step by step.

### Step-by-Step Solution:

1. **Understanding Sieve Cells**:
- Sieve cells are specialized cells found in the phloem tissue of vascular plants. Their primary function is to conduct nutrients, particularly sugars, throughout the plant.

2. **Identifying Lower Vascular Plants**:
- Lower vascular plants include groups such as Pteridophytes (ferns) and Gymnosperms (like conifers). These plants have vascular tissues but are considered "lower" compared to Angiosperms (flowering plants).

3. **Presence of Sieve Cells**:
- In lower vascular plants, sieve cells are indeed present. They are the primary conducting cells in the phloem of these plants, facilitating the transport of food and nutrients.

4. **Comparison with Higher Vascular Plants**:
- In higher vascular plants, particularly Angiosperms, sieve tube elements (which are more advanced than sieve cells) are present. However, this does not negate the presence of sieve cells in lower vascular plants.

5. **Conclusion**:
- Since sieve cells are commonly found in lower vascular plants and play a crucial role in nutrient conduction, the statement is true.

### Final Answer:
**The statement is true. Sieve cells are most commonly found in lower vascular plants.**