How do the pollen grains of Vallisneria protect themselves?

Answer

### Step-by-Step Solution:

1. **Understanding Pollen Grains**: Pollen grains are the male gametes in flowering plants and are crucial for the process of pollination, which is the transfer of pollen from the anthers (male part) to the stigma (female part) of flowers.

2. **Pollination in Vallisneria**: In Vallisneria, a type of aquatic flowering plant, pollination occurs through water. This means that the pollen grains must be able to survive and function in a watery environment.

3. **Protection Mechanism**: To protect themselves from being damaged or saturated by water, the pollen grains of Vallisneria have a special protective covering.

4. **The Protective Coating**: This protective layer is known as the "mucilaginous coating." The mucilaginous coating serves to shield the pollen grains from the effects of water, preventing them from becoming wet and ensuring their viability for fertilization.

5. **Conclusion**: Thus, the pollen grains of Vallisneria protect themselves from water through the presence of a mucilaginous coating that keeps them dry and functional during the pollination process.