Vessels are absent in the xylem of

Options

A. angiosperms
B. monocots
C. gymnosperms excluding gnetales
D. pteridophytes excluding ferns.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the absence of vessels in the xylem of certain plant groups. We need to identify which of the given options lacks vessels in their xylem.

2. **Analyzing the Options**:
- **Option 1: Angiosperms** - Angiosperms are flowering plants and are known to have vessels in their xylem. Therefore, this option is incorrect.
- **Option 2: Monocots** - Monocots are a subgroup of angiosperms, which also possess vessels in their xylem. Thus, this option is also incorrect.
- **Option 3: Gymnosperms excluding Nettles** - Gymnosperms are seed-bearing plants that typically lack vessels in their xylem, with the exception of certain members of the order Netaels (like Natu, Ephedra, and Velvetea). Therefore, this option is correct.
- **Option 4: Pteridophytes excluding Ferns** - Pteridophytes, which include ferns, do not have vessels in their xylem. Hence, this option is also incorrect.

3. **Conclusion**: Based on the analysis, the correct answer to the question is **Gymnosperms excluding Nettles**. This group is characterized by the absence of vessels in their xylem.

### Final Answer:
**Vessels are absent in the xylem of Gymnosperms excluding Nettles.**

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