Mature ................ elements of plants and ……… blood cells of mammals are devoid of nuclei.

Explanation

To answer the question, we need to identify the mature elements of plants and the blood cells of mammals that are devoid of nuclei.

### Step-by-Step Solution:

1. **Identify the Plant Element**:
- In plants, the mature elements that are devoid of nuclei are the **sieve tube elements**.
- These sieve tube elements are a part of the phloem tissue, which is responsible for the transport of nutrients and organic compounds throughout the plant.

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