Dicot roots are usually di-to tetrarch.

Answer

### Step-by-Step Solution:

1. **Understanding Dicot Roots**:
- Dicot roots are characterized by their vascular tissue arrangement. They typically have a specific pattern of xylem and phloem.

2. **Xylem and Phloem Arrangement**:
- In dicot roots, the arrangement of xylem and phloem can be classified as diarch (2 patches) to tetrarch (4 patches). This means that in a cross-section of a dicot root, you can find 2 to 4 distinct groups or patches of xylem and phloem.

3. **Defining Tetrarch**:
- The term "tetrarch" refers to the presence of four patches of xylem and phloem. When a dicot root exhibits this arrangement, it is specifically called tetrarch.

4. **Examples of Dicot Plants**:
- Common examples of dicot plants that exhibit this tetrarch arrangement include gram (chickpeas), sunflower, and castor.

5. **Comparison with Monocots**:
- In contrast, monocot roots have a different arrangement known as polyarch, where there are many patches of xylem and phloem, typically ranging from 6 to 20 patches.

6. **Conclusion**:
- Therefore, dicot roots are usually diarch to tetrarch, indicating the arrangement of their vascular tissues, which is crucial for their function in water and nutrient transport.