In preridophyta, sexual mode of reproduction takes place by _________ .

Explanation

**Step-by-Step Solution:**

1. **Understanding Pteridophyta**: Pteridophyta, commonly known as ferns, are a group of vascular plants that reproduce through spores rather than seeds.

2. **Mode of Reproduction**: The question specifically asks about the sexual mode of reproduction in Pteridophyta. In these plants, sexual reproduction occurs through the formation of spores.

3. **Sporophyte Generation**: In Pteridophyta, the dominant phase is the sporophyte generation. The sporophyte produces sporangia, which are structures that contain spores.

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