To solve the question of identifying the incorrect statement among the given options, we will analyze each statement one by one.
### Step-by-Step Solution:
1. **Analyze the First Statement:**
- The statement claims that algae reproduce vegetatively by fragmentation, asexually by formation of different types of spores, and sexually by formation of gametes.
- **Evaluation:** This statement is true. Algae can reproduce through various methods: vegetative (fragmentation), asexual (spores), and sexual (gametes).
2. **Analyze the Second Statement:**
- The statement states that algae are classified into three classes, pteridophytes into four classes, and angiosperms into two classes.
- **Evaluation:** This statement is also true. Algae are classified into three classes: Chlorophyceae (green algae), Rhodophyceae (red algae), and Phaeophyceae (brown algae). Pteridophytes are classified into four classes: Psilopsida, Lycopsida, Sphenopsida, and Pteropsida. Angiosperms are indeed classified into two classes: monocots and dicots.
3. **Analyze the Third Statement:**
- The statement mentions that algae are chlorophyll-bearing, simple thalloid, autotrophic, and largely aquatic organisms.
- **Evaluation:** This statement is true. Algae are indeed chlorophyll-bearing, simple in structure (thalloid), autotrophic, and primarily found in aquatic environments.
4. **Analyze the Fourth Statement:**
- The statement claims that the plant body of algae is more differentiated than that of bryophytes.
- **Evaluation:** This statement is false. Bryophytes (such as mosses and liverworts) have a more complex structure and differentiation compared to algae. Bryophytes are known as the amphibians of the plant kingdom due to their dependence on water for reproduction.
### Conclusion:
After evaluating all the statements, the incorrect statement is the fourth one: "the plant body of algae is more differentiated than that of bryophytes."
### Final Answer:
The incorrect statement is **the fourth one**.
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