Name the early filamentous structure produced by spore, chiefly in mosses.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the early filamentous structure produced by spores, specifically in mosses.

2. **Identifying the Organism**: We need to focus on mosses, which are non-vascular plants belonging to the group of bryophytes.

3. **Spore Production in Mosses**: Mosses reproduce through spores. These spores are released from the sporophyte generation of the moss.

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