What is the meaning of exarch?

Explanation

### Step-by-Step Solution:

1. **Understanding the Terms**: The term "exarch" is used in botany to describe a specific arrangement of xylem tissues in plants. It is important to differentiate it from its counterpart "endarch."

2. **Xylem Types**: In plants, there are two types of xylem: protoxylem and metaxylem. Protoxylem is the first xylem to develop, while metaxylem develops later.

3. **Arrangement in Exarch**: In an exarch arrangement, the protoxylem is located towards the periphery (outer part) of the plant structure, while the metaxylem is situated towards the center. This means that the development of the xylem is directed inward, which is referred to as centripetal development.

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