Pollen grains of Pinus are......

Explanation

**Step-by-Step Solution:**

1. **Identify the Subject**: The question is about the pollen grains of Pinus, which is a genus of coniferous trees.

2. **Understand the Characteristics of Pinus**: Pinus trees are evergreen conifers, meaning they retain their leaves throughout the year. They have well-developed structures such as roots, stems, and leaves.

3. **Define Pollen Grains**: Pollen grains are the male gametophytes (also known as microgametophytes) that are produced in the male reproductive structures of plants. In flowering plants, these structures are called stamens.

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